So, can DC pass through an Inductor or Capacitor?

DC can pass through an Inductor, but not through a Capacitor. In DC circuits, when fully charged a capacitor behaves like an open circuit not allowing current to pass, whereas an Inductor behaves like a short circuit allowing current to pass. 

What is DC?

All electronic circuits need current to operate. Current is like blood coursing through our body. Just like how it is essential that our bodies need blood to live, so too is it important for electrical and electronic circuits to have current to operate.

There are two types of current that can flow in electrical and electronic circuits; Direct Current (DC) and Alternating Current (AC). 

The main difference between Direct Current and Alternating current is the direction of flow. DC flows in one direction, while AC flows in both directions.In AC circuits the voltage also follows the current. 

DC is best represented with a steady straight line, and AC with a ‘alternating’ waveform like a sinusoidal wave (as seen in the images below).

What is a capacitor?

The electrical and electronic world is filled with a range of different components each having their own set of unique characteristics that help in different applications. One of the most widely used is the Capacitor. A capacitor is a two terminal electronic component that has the ability to store energy in the form of an electrical field when voltage is applied to it. 

The capacitor consists of two terminals connected to two metal plates. These metal plates are separated by an insulating material known as a Dielectric. The insulating material could be a range of materials such as glass, ceramic, mica, or even air. 

What happens when you connect a capacitor to a battery?

When a voltage is applied across the terminals of the capacitor, the metal plate connected to the negative terminal of the capacitor starts to attract electrons (making it negatively charged), while the plate that is connected to the positive terminal of the battery starts losing electrons (making it positively charged).

Once fully charged, the voltage across the capacitor will equal the voltage of the power supply it is connected to.

What is an Inductor?

An Inductor is another widely used component in electronic and electrical circuits. An Inductor is also a two terminal component which has the ability to store energy in the form of a magnetic field when current flows through it. It consists of an insulated wire which is wound into a coil. Many Inductors are accompanied by a magnetic core made of Iron to help increase the strength of the magnetic field.

The strength of the magnetic field can also be increased by several other factors which include the number of turns of the wire, diameter of the coil, coil length, and layers of winding in the coil. 

When an ‘changing’ current is applied to an Inductor, the magnetic field acts to oppose this change in current by producing a voltage known as an Electromotive Force (EMF) . This voltage has a polarity which opposes the change in current. In short, Inductors oppose change in current. 

Why does an Inductor allow DC to pass?

Now that we have learnt the basics of a Capacitor and Inductor, we can understand better why an Inductor allows DC to pass, but a Capacitor blocks it.

As we just saw above, an Inductor opposes changes in current. When current changes within an Inductor, it produces a voltage (EMF) of equal force to oppose this change in current. We know that DC is a steady current in one direction whose magnitude does not vary with time. Therefore, when DC is applied to an Inductor it does not offer any resistance (EMF), and acts like a short circuit allowing DC to pass. 

Why does a capacitor not allow DC to pass?

This comes down to what we learnt earlier about capacitors.

When voltage is first applied to the capacitor, a small current flows until both plates become saturated.This indicates that the voltage across the capacitor equals the supply voltage. At this point no more current can flow and is essentially an open circuit. This is why a Capacitor blocks DC. 

Increasing the voltage further will damage the capacitor. 

Why are capacitors used in DC circuits if they block it?

If capacitors block DC, why can you find them in so many DC circuits? Even though they block DC we can use that ability to good effect in DC applications. This comes down to the fact that it takes time to fully charge a capacitor. This unique ability can be used to great effect in DC circuits to reduce noise in power supplies and reduce high voltage transients. It is very common (and advised) to place a capacitor across an IC’s (Integrated Circuits) supply to source current which helps in avoiding drops in voltage. They are also found in rectifiers to smooth out voltage ripples from AC inputs.

The post Can DC pass through an inductor or capacitor? appeared first on Electronic Guidebook.

So, what is the main difference between a resistor, capacitor and inductor?

The main difference between a resistor, capacitor and inductor is what each does with energy. A resistor dissipates energy in the form of heat, a capacitor stores energy in the form of an electric field, and an inductor stores energy in the form of a magnetic field. Also, each of these components have different functions which play an essential role in electrical and electronic circuits. This article shall take a more in-depth look at each of these.

The resistor, capacitor and inductor

Before we take a look at the differences between these three components, let’s take a brief look at each component to see what they are all about.

What is a resistor?

Of the three components, the resistor is the most commonly used. The resistor plays a vital role in electrical and electronic circuits. Its main purpose is to limit the flow of current. It does this by providing a resistance to the flow of current. The greater the resistance, the less current can flow, and the lower the resistance, the more current can flow. Current is a form of electrical energy and when it flows through a resistor, this energy is converted into heat energy (which is dissipated into the surroundings). 

Other than just limiting current, a resistor can be used for many other purposes which include, voltage division, heat generation, matching and loading circuits, gain control and setting time constants. 

What is a capacitor?

Next up we have the capacitor. A capacitor is composed of two conducting plates that are separated by a dielectric (which is an insulating material). The main purpose of a capacitor is to store energy in the form of electrical energy. This stored energy can be released back into the circuit when required. The amount of electrical energy a capacitor is capable of storing is determined by its capacitance. The higher the capacitance, the more energy it can store, and vice versa. Capacitors allow Alternating Current (AC) to pass, but block Direct Current (DC).

Other than energy storage, capacitors are used for power conditioning, noise filtering, remote sensing, and signal coupling/decoupling. 

What is an inductor?

Last, but not least, is the Inductor. Inductors, also sometimes referred to as a coil or choke, are an electronic component that stores energy in a magnetic field when current flows through it. They are constructed using an insulated copper wire that is wound into a coil around a core (which is usually magnetic iron or ferrite). Inductors also have the ability to oppose changes in current which is determined by their Inductance. The higher the inductance the more effective an inductor is at opposing changes in current. Because of this fact, inductors block AC, but allow DC to pass. A wire with more coils (turns) is going to have a higher inductance. 

The applications of inductors include; choking, blocking, attenuating, filtering/smoothing high frequency noise, storing and transferring of energy. 

What is the difference between a resistor, capacitor and inductor?

The main difference between a resistor, capacitor and inductor, is what happens with current flowing through them. Energy is the common theme they share, however, what happens with energy in each of them varies. When current flows through a resistor, energy is dissipated in the form of heat. In a capacitor energy is stored in the form of an electric field when current flows through it. And when current flows through an inductor, energy is stored in a magnetic field. 

Other than that, the other major differences between these components include;

• Main functionality
• Construction

Main functionality

Other than what each does with energy, the other difference between a resistor, capacitor and inductor, is the main functionality and the applications they are used in. The main function of a resistor is to limit current, whereas the main function of a capacitor is to store charge for later use and the inductor’s primary purpose is to oppose any change in current. As there is a difference in their functionality, so too are the applications they will be used for.

Construction

How a resistor, capacitor and inductor is constructed is another difference. As we just saw, each has a different function. They get these unique functions due to the way that they are constructed (as well as the materials that they are constructed with). 

Difference between a capacitor and inductor

Of the three components, the capacitor and inductor are quite similar in that they both store energy. But, the way they store energy is their major differentiation. A capacitor stores energy in an electric field, while an inductor stores energy in a magnetic field. But, there is another difference between these two components. 

There are two types of current that can flow through an electrical/electronic circuit. The current can either be an Alternating Current (AC) or a Direct Current (DC). When it comes to a capacitor, it blocks Direct Current, but allows Alternating Current to pass. Inductors on the other hand allow Direct Current to pass, but block Alternating current.

Summary of the differences between a resistor, capacitor and inductor

Below is a table summarising the differences between a resistor, capacitor and inductor. 

The post What is the difference between a resistor, capacitor, and inductor? appeared first on Electronic Guidebook.

These two components share a similar ability, which is to store energy. This is why sometimes they can be confused for being the same.

However, each of them goes about doing so in different ways. 

The major differences between a capacitor and inductor include:

• Energy storage 
• Opposing current vs Opposing voltage
• AC vs DC
• Voltage and current lag
• Charging and Discharging rates
• Applications
• Units

This article shall take a closer look at all these differences between the capacitor and inductor. 

Deeper look at a capacitor and inductor

To better understand the differences between the two components, it will benefit you to first learn a bit more about each component individually. 

Things like their purpose, working principle, construction, etc. 

However, if you already have a knowledge of both components, you can skip straight to the capacitor vs inductor section. 

Let’s start with the capacitor.

What is a capacitor

Capacitors are one of the three fundamental passive components used in electrical and electronic circuits (the other two being resistors and inductors).

A capacitor is a two terminal passive component which has the ability to store electrostatic energy within an electric field when current flows through it.

The main purpose of a capacitor is to oppose changes in voltage. 

They have many applications in a circuit with the most common being energy storage, voltage spike suppression and signal filtering. 

There are two types of capacitors; Polarised and Non-Polarised. 

A non-polarised capacitor is like a resistor and the orientation of its terminals does not matter when placing it in a circuit. 

Polarized capacitors however, have a positive and negative terminal, which means that they must be placed the right way round in a circuit.

Construction of capacitor

A capacitor is constructed using two metal plates which are separated by an insulating material known as the dielectric as seen in the diagram below.

The dielectric can be a range of insulating materials (inhibits the flow of current) which can include;

• Air
• Paper
• Glass
• Rubber
• Plastic 
• Ceramic

While the two metal plates are made from conductive materials (allows the flow of current) and can include metals such as;

• Aluminium
• Tantalum
• Silver
• Copper

Working principle of a capacitor

The simplest form of a capacitor is two metal plates separated by a dielectric as we saw earlier.

When a voltage is applied to a capacitor, an electron is added to one plate making it negatively charged.

This electron has an electric field which repels other electrons. It travels through the space between the plates and bumps the electrons off the other plate making it positively charged.

As the process increases, the amount of electrons added to the first plate increases thus increasing its negative charge, which in turn increases the induced positive charge on the second plate. 

Eventually, the amount of negative charge on the first plate is going to reach a maximum value which will prevent the battery from adding more electrons.

The capacitor is said to be fully charged at this point, and its electric field will be at its strongest. 

Since electric fields radiate away from positive charges and towards negative ones, an electric field will point across the gap between the two metal plates in straight lines. 

How much energy is stored within a capacitor’s electric field

When a capacitor is connected to a power source (like a battery), it stores the received energy in the form of the electric field which we have just discussed. 

The amount of energy stored in a capacitor’s electric field comes down to a singular formula and a couple of variables. 

Without going into too much detail of its derivation, below is the formula used to calculate the amount of energy stored within a capacitor’s electric field. 

W represents energy, C is capacitance and V is voltage. 

Let’s take a look at how capacitance affects the magnitude of a capacitor’s electric field. 

Capacitance is a crucial part of a capacitor which determines its ability to store electrical energy in an electric field.

As you just saw before, when a voltage is applied to a capacitor, a fixed amount of positive (q+) and negative (q-) charges build up on either plate of the capacitor. 

Using the value of voltage (V) and total amount of charge (q), we can calculate the total capacitance (C). 

What is an inductor

Now let’s learn about the Inductor.

While not as common as the resistor or capacitor, inductors are still widely used in many electrical and electronic circuits for their unique abilities.

An inductor is a two terminal passive component which has the ability to store energy in the form of a magnetic field when current flows through it.

The main purpose of an Inductor is to oppose any sudden changes in current. 

They slow down current spikes and surges by storing this extra energy in their magnetic field and then slowly releasing it back into the circuit.

Its ability to resist this change can be shown by its Inductance which is the ratio of voltage and current change within the inductor. 

Inductance is given in the unit of Henry (H). 

Construction of inductor

If you were to look at a circuit schematic which had an inductor, you would see a symbol as seen below. 

The construction of a basic Inductor involves a wire that is coiled around a core material. 

This core material can vary depending on the needs of the application and can include either magnetic iron or ferrite core (amongst the most common).

An insulated copper wire is the choice of material for the wire wrapped around the core. 

There are many variables that can alter the inductance of an inductor which include; number of turns (of the wire), spacing between turns, number of layers of turns, material of core, magnetic permeability of core material, size, and shape. 

Working principle of a inductor  

So how does an inductor work?

As we just saw, an inductor is composed of a wire coiled around a core. The working principle of an inductor can be better understood if we uncoil this wire into a straight wire.

When current flows through a straight wire, a magnetic field is generated around that wire as can be seen in the image below.

The strength of the magnetic field is directly proportional to the current. So, increasing the current will increase the magnitude of the magnetic field.

Also, the strength of the magnetic field is strongest closest to the wire. An inductor utilises this concept. It consists of wire wrapped in a coil formation around a central core.

This means that when current flows through the inductor, a magnetic field is generated within the inductor. 

Since the wire is coiled, the magnetic field is multiplied. 

The relationship between current and the strength of the magnetic field are directly proportional. So, an increase in current will see an increase in the strength of the magnetic field.

How much energy is the inductor capable of storing?

As you can imagine, the amount of energy stored in the magnetic field of a straight wire is going to be far less compared to that of a wire that has been coiled.

This is due to the fact that the magnetic field (and therefore magnetic energy) is increased as a straight wire is coiled.

The strength of a magnetic field around a straight and coiled wire is known as magnetic field strength or H.

Below are the two formulas for the H in a straight and coiled wire.

H – strength of magnetic field ampere/turn

N – number of turns of coil

I – current flowing through in Ampere (A)

L – length of coil (in metres)

By looking at the equation for a straight wire you can see that the only way to increase the magnetic strength is to increase the amount of current, or material of wire.

However, when it comes to a coil, you have many more options to increase magnetic strength which include;

• Number of turns contained within the coil
• How much current is flowing 
• Type of core material used for the inductor
• Cross sectional area of wire

Capacitor vs Inductor -7 key differences 

Now that we know a bit more about both the capacitor and inductor, we can have a discussion about the key differences between the components. 

Capacitor vs Inductor key difference #1: Energy Storage

The first key difference between a capacitor and inductor is energy storage.

Both devices have the capability to store energy, however, the way they go about doing so is different. 

A capacitor stores electrostatic energy within an electric field, whereas an inductor stores magnetic energy within a magnetic field. 

Capacitor vs Inductor difference #2: Opposing current or voltage  

As we just saw, both devices have the ability to store energy either in an electric field (capacitor) or magnetic field (inductor).

This energy storage has a purpose which is to either oppose current or oppose voltage. 

A capacitor opposes changes in voltage, while an inductor opposes changes in current. 

Capacitor vs Inductor difference #3: AC or DC   

Electrical and electronic applications can be divided into two major categories; Alternating Current (AC) or Direct Current (DC).

Alternating Current deals with current whose direction and magnitude varies periodically (just like a sinusoidal wave).

Direct Current on the other hand has only one direction and magnitude. It does not change periodically. 

When it comes to capacitors and inductors, each deals with these currents differently. 

Capacitors allow AC currents to pass, but prevents DC currents from flowing.

Inductors on the other hand allow DC currents to pass, but block AC.

Capacitor vs Inductor difference #4: Voltage and Current Lag   

When current flows through a circuit it is going to encounter three types of impedances (opposition), which are caused by Resistance (R), Inductance (L), and Capacitance (C). 

Resistance does not pose much opposition so voltage and current are in phase.However inductors and capacitors do provide impedances which offset voltage and current. 

When voltage rises in a circuit that has an inductor, a rise in voltage sees a rise in current. This rise is slightly delayed due to Back EMF caused by the inductor. 

This means as voltage rises and falls, current rises and falls a fraction of a second later. 

So current lags voltage in an Inductor. 

The story is much different for circuits that contain capacitors. When current rises, voltage rises, but when it falls, the fall of voltage is slightly delayed.

So voltage lags current in a capacitor. 

Capacitor vs Inductor difference #5: Charging and discharging rate

So, capacitors store electrical energy, and inductors store magnetic energy. However, this energy build up does not happen instantaneously. 

Also, the release of energy takes time.

The build up, and release of energy for a capacitor and inductor are known as their charging and discharging rates respectively. 

A capacitor’s charge and discharge rate is governed by the RC Time Constant, whereas an inductor’s charge and discharge rate is given the RL Time Constant.

Where R is the value of the resistor in series with the components, C is the capacitance and L is the inductance. 

Capacitor vs Inductor difference #6: Applications

Both the capacitor and inductor have unique abilities. 

This means that each component will have its own unique purpose for certain applications. Below shows the different applications for a capacitor and inductor.

Capacitor applications:

• Power conditioning
• Signal coupling/decoupling
• Noise filtering
• Remote sensing
• Power factor correction

Inductor applications:

• Choking
• Blocking
• Attenuation
• High frequency noise filtering/Smoothing
• Energy transfer (DC-DC or AC-DC)

Capacitor vs Inductor difference #7: Units

The last major difference between a capacitor and inductor is their Units.

Units are found in every aspect of science and engineering. It defines the magnitude of quantity which is brought about by convention or law. 

This unit will be universally recognised. 

For example, the unit for current is Amperes (Amps), represented by the letter I.

The amount of energy a capacitor is capable of storing is dependent on its Capacitance (C), which has the units of Farads further represented by the letter F.

While the amount of energy an inductor is able to store is dependent on its Inductance (L), which has the units of Henry with the symbol H. 

Do a capacitor and inductor share any similarities?  

We have just seen the major differences between a capacitor and inductor. But, these two components do share some similarities in their overall purpose.

The first thing in common is that both components have the ability of storing energy even if the type of energy stored is different.

Next, both components use this stored energy to oppose the rise of a force, voltage for a capacitor, and current for an inductor. 

Finally, both components have charging and discharging rates. This means that voltage and current does not change instantaneously for either. 

Which is better; a capacitor or inductor?

A capacitor is not better than an inductor, and an inductor is not better than a capacitor. 

As you have just seen, while both components share a similar purpose (energy storage), they differ in many other characteristics.

Their differences are what gives each of them unique abilities for different applications. 

So, it really depends on the needs of the application. You cannot say one is better than the other. 

Can you use a capacitor and inductor together?

Yes, a capacitor and inductor are commonly used in the same circuit. 

An LC circuit is a circuit that contains an inductor and capacitor which is also commonly known as a tuned, tank, or resonant circuit. 

This type of circuit has the specific purpose of generating signals at a particular frequency, or to receive a complex signal at a particular frequency. 

Common applications for LC circuits include radios, radio equipment, tuners, filters, frequency mixers and oscillators.

The post Capacitor vs Inductor - 7 key differences appeared first on Electronic Guidebook.

Knowing the possible reasons as to why a capacitor might explode will save you stress and money (as you won’t have to keep replacing blown capacitors). 

So, what would cause a capacitor to explode? The main two reasons that would cause a capacitor to explode is Reverse polarity voltage and Over-voltage (exceeding the voltage as little as 1 – 1.5 volts could result in an explosion). Electrolytic capacitors are more susceptible to explode as opposed to other types of capacitors. 

This article will dive deeper into Reverse polarity voltage and other possible reasons as to what can cause a capacitor to explode. 

Deeper look at the capacitor

Understanding the construction of the capacitor will give us a better insight into the question at hand, as to what could possibly cause it to explode. 

A capacitor is an electronic component designed to store energy in an electric field. 

Capacitors are constructed with a Dielectric that is sandwiched between two Conducting plates.

The dielectric is an insulating material. Materials used for a capacitor’s dielectric can range from glass, ceramic, plastic film, paper, mica, air and oxide layers.

A conductor is needed for the two plates which can range from; metals, thin film, foil, or an electrolyte. 

Capacitance of a capacitor

How much energy a capacitor can store is determined by its Capacitance which is measured in Farads (F).

A capacitor with a higher value of capacitance can hold much more charge than one with a smaller value. 

The magnitude of capacitance of a capacitor is largely influenced by its physical construction. So, the larger the area of the plates the higher it’s capacitance. 

Other factors that influence the capacitance of a capacitor are;

• Separation of plates (the closer the plates the higher the capacitance)
• Dielectric material ( the higher the Dielectric constant the higher the capacitance

Capacitor voltage

Another important parameter of a capacitor is its Voltage.

This value of a capacitor defines the maximum voltage it can withstand without any failure. It is a measure of the strength of its dielectric insulation. 

Every capacitor has a voltage rating which is printed on the capacitor.

If it is not printed on the capacitor, it can be found on its datasheet. 

Different types of capacitor

When it comes to capacitors, there are many different types available, with each being beneficial for different electrical and electronic applications. 

Again, the type of capacitor is largely influenced by how it is constructed and what kind of dielectric it uses. 

Below are some of the most common types;

• Electrolytic capacitor 
• Mica capacitor 
• Paper capacitor 
• Film capacitor 
• Ceramic capacitor

Polarized vs Non-Polarized capacitors

Another distinction between different types of capacitor are their polarity. 

Capacitors can either be Polarized or Non-Polarized.

A capacitor that has no polarity (non-polarized) can be wired up in a circuit either way.

However, a polarised capacitor can only be wired one way. 

It has one positive terminal and one negative terminal.

So, connecting a polarised capacitor requires more care as its terminals need to be connected the right way right in a circuit. 

What type of capacitor is more likely to explode?  

When it comes to a capacitor exploding, the electrolytic capacitor is the most likely type to cause a spectacle compared to its counterparts. 

Other capacitors will not explode, but rather burn, crack, pop or smoke. 

The main reason why an electrolytic capacitor might explode is due to its construction.

As we saw earlier, the bigger the capacitor the more capacitance it will have. But, sometimes this is impractical, as you might require a smaller sized capacitor with high capacitance. 

One way of doing that is to bring the conducting plates of the capacitor closer together. But, again we encounter another problem in that the voltage rating gets a bit impractical.

Electrolytic capacitors were developed to combat this issue. 

Internal construction of electrolytic capacitors

They are designed to achieve high capacitance in smaller packages, with small separations of plates as well as reasonable voltages.

Rather than using an insulating material for the dielectric, the insulating layer is created by an oxide layer that is formed through a process known as anodization of the anode (positive plate) of the capacitor.

The oxide layer ends up being a thin film and is how both the plates can be closer together. 

This process is repeated for the cathode (negative plate). 

The electrolytic capacitor has an anode and cathode as it is polarised. 

Between the two plates is a paper separator soaked in a water based solution. The solution (also known as an electrolyte) has an alkali added to it to make it a conductor. 

So why does an electrolytic capacitor explode?

When an electrolytic capacitor breaks down (due to factors I will discuss below), the oxide layer breaks down.

This causes high amounts of current to pass through the electrolyte. 

High amounts of current will result in high amounts of heat. This high heat will vaporize the water into a  gas which causes a build of pressure in the capacitor causing it to explode. 

For this reason, electrolytic capacitors are created with a fail safe which is a split in the capacitor that helps vent the gas in a more controlled manner. 

Factors that would cause a capacitor to explode

Let’s dive into the factors that can cause a capacitor to explode.

Note, as mentioned earlier, electrolytic capacitors are more likely to explode. But, these factors will still cause other types of capacitors to fail as well, only with no explosion.

Factor #1 that would cause capacitor to explode: Reverse Polarity

The first factor that is most common and likely to cause a capacitor to explode is, Reverse Polarity.

Reverse polarity applies for components and devices that are polarised. 

As you saw earlier, an electrolytic capacitor is a polarised component that has a positive and negative terminal which means it needs to be wired the right way in a circuit. 

Reversing the polarity of a capacitor means that you wire it the wrong way in a circuit (the positive terminal gets connected to negative, and the negative terminal gets connected to positive).

If you happen to wire it the wrong way and apply a voltage for a very short amount of time, it shouldn’t be much of  a problem. 

However, longer durations when exposed to reverse polarity will cause an electrolytic capacitor to explode. 

Factor #2 that would cause capacitor to explode: Over voltage

The next factor that might cause a capacitor to explode is Over voltage.

A capacitor is designed to hold a certain amount of capacitance as well as withstand certain amounts of voltages and currents. 

The voltage of a capacitor is usually displayed on the outside of its packaging. 

Exceeding these voltages can cause the dielectric to fail which results in large currents flowing.

These large currents cause large amounts of heat and thus destroy the internal structure of a capacitor.

As we saw earlier, with electrolytic capacitors, the water boils turning into steam which builds up pressure resulting in an explosion. 

Over voltage or current might be caused by human error. Where the person might supply voltages past the capacitors limit. 

Or, it could be caused by a power surge. 

Factor #3 that would cause capacitor to explode: Storage

This next factor pertains more to electrolytic capacitors and comes down to their storage. 

Electrolytic capacitors do not store very well.

Their voltage rating drastically reduces the longer they are stored for as their internal chemistry deteriorates.

This could cause a capacitor to explode as it might display a certain voltage, but its actual voltage has reduced. So when you apply a voltage as displayed it will be higher than the actual voltage causing it to explode. 

Can a capacitor that has exploded still work?

Unfortunately a capacitor that has exploded will not work.

The internal composition of a capacitor is designed specifically to store an electric field.  

An explosion would  ruin the internal composition thus rendering the capacitor useless. 

How to prevent a capacitor from exploding

A capacitor that explodes can be a frightful experience!

So, the less explosions the better. Also, this will save you a lot of money not having to constantly replace them.

Below are some things you can do to prevent a capacitor from causing destruction.

Reverse Polarity – If you are using polarised capacitors (like an electrolytic capacitor), double check, no triple check that you have wired it the right way before applying a voltage.

Over voltage – This might be a simple solution be it’s worth noting, stay within the limits of the capacitors voltage ratings. 

Storage – Avoid storing electrolytic capacitors for long periods of time. If you are going to use one that has been stored away for a long time, test that it can still withstand the voltage it was designed for.

The post What would cause a capacitor to explode? appeared first on Electronic Guidebook.

A capacitor is an electrical component that generates an electric field between its plates when a voltage is applied to its terminals. 

This electric field can then store electrical energy which can be used later. 

How much electrical energy a capacitor can store is determined by its Capacitance. 

The higher the capacitance, the more energy it can store and vice versa. 

But, should capacitors have continuity? Capacitors should not have continuity. However, when testing the capacitor using the continuity function of a multimeter you might get intermittent ‘beeping’ due to the capacitor charging and discharging. Note, this does not indicate that the capacitor has continuity. 

If there is a constant ‘beeping’ from the multimeter, this shows that there is continuity in the capacitor which means that it is faulty. 

Read on for more information why a capacitor should not have continuity. 

Brief look a the capacitor

Let’s take a brief look at the capacitor, which will give you a better understanding as to  why it should not have continuity. 

Capacitors are one of the three fundamental passive components used in electrical and electronic circuits (the other two being resistors and inductors).

As mentioned above, the capacitor has the ability to store energy in its electric field. 

They have many applications in a circuit with the most common being energy storage, voltage spike suppression and signal filtering. 

There are two types of capacitors; Polarised and Non-Polarised. 

A non-polarised capacitor is like a resistor and the orientation of its terminals does not matter when placing it in a circuit. 

Polarised capacitors however, have a positive and negative terminal, which means that they must be placed the right way round in a circuit. 

The basic construction of a capacitor

A capacitor is constructed using two metal plates which are separated by an insulating material known as the dielectric as seen in the diagram below.

The dielectric can be a range of insulating materials (inhibits the flow of current) which can include;

• Air
• Paper
• Glass
• Rubber
• Plastic 
• Ceramic

While the two metal plates are made from conductive materials (allows the flow of current) and can include metals such as;

• Aluminium
• Tantalum
• Silver
• Copper 

What is electrical continuity

Say you are crossing a bridge over a river.

If you can get from one side of the bridge to the other without falling into the river, the bridge’s path is said to be Continuous.

Now, imagine there is an earthquake which splits the bridge in half. 

You will not be able to cross the bridge safely as the path is no longer continuous

Electrical continuity pertains to the electrical and electronics world which states that for current to flow, it requires a complete path. 

In the above analogy the bridge would represent an electrical wire, and you crossing the bridge would represent the electrons flowing through that wire. 

Just like our analogy, if there is a break in the path the electrons will not be able to flow from one end of the wire to the other. 

What materials have electrical continuity

Electrical continuity exists in materials that are conductive. 

A conductive material is something that is effective at transferring or ‘conducting’ heat and electricity. 

This means electrons are loosely bound to their atoms within the material allowing them to move more freely.

Metals are very effective conductors  and are the main reason they are used in electrical and electronic circuits. 

Metals such as copper, silver, gold, tin, lead etc.

Insulators on the other hand are poor conductors. 

The electrons of the atoms within the material are held more tightly making it harder to transfer electrons (electricity and heat).

Continuity of the Multimeter

The multimeter is an electronic measuring instrument that is used daily for troubleshooting and analysing electrical and electronic circuits. 

Depending on the complexity of the multimeter, it can have the following functionalities;

• Read DC voltage
• Read AC voltage
• Test current
• Measure resistance
• Check diodes
• Transistor testing
• Continuity

The most basic of multimeters will have the ability to test continuity which is what we are concerned with. 

The continuity symbol on a multimeter is shown using a sound wave (like that emitting out of a speaker symbol), as it uses a beeping sound to indicate continuity. 

So how do you test continuity using a multimeter? 

Say you have a piece of wire (like in the picture below), and you want to test whether that piece of wire is continuous from one end to the other.

1. First set the multimeter to the continuity setting
2. Place one probe (negative or positive. The polarity does not matter), on one end of the wire (if the wire is insulated you will need to strip it first and place it on the conductive part of the wire).
3. Place the second probe on the other side of the probe.
4. If the wire has continuity the multimeter will produce a constant ‘beep’. 
5. If there is no continuity, there will be no beep

Note, if the material is somewhat conductive, there won’t be a beep but a resistance which will be displayed on the screen.  

Why a capacitor should not have continuity 

Now that we know the construction of a capacitor and how continuity works, we can take a look at why a capacitor should not have continuity.

The multimeter will only beep when a path is conductive and continuous. 

We saw that a capacitor consists of two metal plates separated by an insulating material, therefore a continuous, conductive path does not exist within the capacitor therefore it will not have continuity.

However, you might get intermittent beeping when first testing a capacitor.

This happens because the multimeter uses a small current to test resistance (and continuity is pretty much a really low resistance reading).

So when the probes are placed on the capacitor, the capacitor will start charging (due to the current) causing the beeping sound due to a small resistance present.

But, this does not mean that the capacitor has continuity. 

What happens if a capacitor does have continuity

If for some reason your multimeter has a constant beep when testing the continuity of a capacitor, this could indicate that the capacitor is faulty. 

If the dielectric inside the capacitor has ruptured causing the metal plates to touch, this will create a continuous path. 

But, you will not be able to use the capacitor anymore. 

How to protect capacitors from getting continuity

A faulty capacitor might have continuity as the two metals inside might be touching. 

But, this is not good as you will not be able to use the capacitor again.

There are couple reasons a capacitor might become faulty;

Static electricity 

If you handle the capacitors without an Antistatic Wrist Strap you run the risk of damaging it through static electricity. 

An Antistatic Wrist Strap reduces or removes electrostatic discharge which is the buildup of static electricity. 

Static electricity can damage electronic equipment like computer hard-drives and even ignite flammable liquids.

Exceeding maximum voltage and current ratings

Every capacitor has a maximum voltage and current rating.

These ratings let you know what maximum values of voltage and current it can handle before failure. 

So, be sure to check your capacitor ratings and stay below them.

The post Should capacitors have continuity? appeared first on Electronic Guidebook.

They are very similar to a battery, as they store electrical energy in the form of an electrical field. 

Capacitors come in a variety of shapes, sizes and materials (used for the dielectric) which can include Mica, Ceramic, Mylar, Teflon and even air. 

Another thing that varies between capacitors is their capacity (how much charge they can hold), also known as capacitance. 

Farad is the derived unit of electrical capacitance. It can be defined as the ability of a capacitor or body to store electrical charge.

But, can you replace a capacitor with a lower uf capacitor? Replacing a capacitor with a lower uf one depends on the circuit that the capacitor is being used in. In general the value of the capacitor has been chosen specifically to meet a certain function in the circuit. Replacing a capacitor with a lower uf might affect the circuit in unwanted ways. 

I shall cover this in a bit more detail in this article. 

What is the capacitor uf?

Let’s take a closer look at the capacitance of capacitors. 

As mentioned earlier, Farads is the unit that determines a capacitors storage potential or capacitance. 

A capacitor that is 1 Farad, is said to have the ability to store one coulomb of charge at 1 volt, where 1 coulomb equals 6.25 x 10¹⁸ electrons.

A 1 Farad capacitor would require a pretty big packaging to be able to store that amount of charge. 

Capacitors come in smaller Farad values that include milli-farad (mF), micro-farad (uF), nano-farad (nF) and pico-farad (pF). 

As the capacitance of the capacitor decreases, so does the size of the capacitor and its Farad value and vice versa.

Applications of a capacitor

The capacitor has many uses in a circuit apart from just storing charge which can include;

• Eliminating ripples 
• Blocking DC voltage
• Smoothing output of power supplies 
• Tuning of frequencies in resonant circuits 
• Stabilizing voltage and power flow in electric power transmission
• Coupling
• Decoupling
• Motor Starters
• Energy Storage
• Power Factor correction
• High-pass and Low-pass filters
• Noise Filters and snubbers

Can you replace a capacitor with a lower uf?

If you are wanting to replace a capacitor with a lower uf one, there are many things to consider before doing so. 

Different capacitor values will have different functions in each of the applications mentioned above.

So, lowering the uf value might cause the circuit to not function correctly or even stop working altogether. 

Below are some effects lowering the uf of a capacitor can have on different circuits.

Resonant circuit – you will most likely change the resonant frequency thereby rendering the system useless. 

Timer circuit – lowering the uf of the capacitor will affect the timing intervals which could be good or bad depending on the needs of the application

Motor or light dimming circuit – Depending on how much you lower the capacitance, the results can vary

Feedback loop (Amplifier circuit) – This again would affect the workings of the circuit considerably, as the values of the capacitor are chosen specifically.

The rule of thumb is if the capacitor value plays a part in things like tuning or timing of a circuit, it is best to not lower the capacitance. 

Sure, lowering the uf by a little might not have considerable effects but, these small changes will add up in the end. 

Other considerations when replacing a capacitor with a lower uf 00

There are some other factors to be mindful of when replacing a capacitor with a lower uf. 

These include the Voltage and Type of Capacitor. 

Capacitor voltage

Other than having a capacitance rating (Farads), capacitors have a voltage rating as well. 

This rating specifies the maximum voltage a capacitor can handle before failure (which can sometimes be a mini explosion).

When designing a circuit, capacitors are chosen with voltage ratings that match or are little larger than the voltages expected in the circuit. 

The rule of thumb is to select capacitors with voltage ratings higher than those expected in the circuit as a buffer.

So, if you decide to replace a capacitor with a lower uf one, make sure that the new capacitor has the same voltage rating of the one you are replacing or is larger. 

Types of capacitor

The main construction of a capacitor involves two electrical conductors (plates), separated by an insulating material known as a Dielectric. 

The metal plates can range from thin metal films, aluminium foil, or disks.

The dielectric can be any insulating material which ranges from glass, ceramic, plastic film, air, paper, mica etc. 

Also, other than the materials used, capacitors vary in how they are constructed which include;

• Wrap and Fill (Oval and Round)
• Epoxy case (Rectangular and Round)
• Metal Hermetically Sealed (Rectangular and Round)
• Radial Lead type
• Axial Lead type

Below are the different types of capacitors available varying in construction and materials used

• Ceramic
• Electrolytic
  • Aluminium Electrolytic or Tantalum Electrolytic
• Mica
• Polarized
• Non-Polarized
• Polyester
• Polypropylene
• Polystyrene

As you can see there are many varieties of capacitors available for use.

However, each type of capacitor behaves differently when used in different circuits. 

So, when you are deciding to replace a capacitor with a lower uf one, you will have to make sure that the capacitor type can be suitable in the circuit.

Below are some common rules for different types of capacitors that will help you when you are replacing a capacitor:

• Foil wound capacitors will have more series inductance than ceramic capacitors
• Tantalum capacitors are more sensitive to inrush currents, so avoid replacing an aluminium electrolytic capacitor with a tantalum capacitor
• Cannot use a polarised capacitor in AC applications

Another note to make is whether the capacitor you are replacing is polarised or not. 

If it is polarised, you will need to make sure the replacement capacitor is polarised as well. 

Can you replace a capacitor with a higher uf?

Again, just like replacing a capacitor with a lower uf, it all depends on the function of the capacitor in the circuit.

If the capacitor value was chosen specifically for timing or tuning purposes, increasing the capacitance might affect the circuit’s functionality. 

In some instances the effects can be minor, or they could be quite large. 

Also, always consider the voltage of the capacitor as well as what type of capacitor it is.

The post Can you replace a capacitor with a lower uf? appeared first on Electronic Guidebook.