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.

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So, what exactly is the difference between an Inductor and Inductance? Inductance is the characteristic of a conductor to oppose changes in current by producing an electromotive force.  An Inductor is an electronic device whose main purpose is to oppose changes in current in a circuit by utilising inductance. The inductance of an inductor can be altered by changing its physical properties which include the core material used for the inductor, increasing the cross sectional area of the magnetic core, and increasing the number of turns of the coil. 

What is inductance?

Conductors have many different properties which include electric resistivity, magnetic permeability, conductivity, malleability, ductility, thermal conductivity, etc. Another important property of a conductor is its Inductance, which defines the ability of the conductor to oppose changes in current in the form of an electromotive force or voltage. The units of the inductance are given in Henrys (named after Joseph Henry who first discovered inductance) denoted by H. However, you might also associate inductance with the letter L. One Henry causes a Voltage of one volt, when current is changing at a rate of one ampere per second.  The inductance of an inductor is largely influenced by the cross-sectional area of the conductor, as well as the magnetic permeability of nearby materials. 

Below is the formula for inductance for a coil of wire;

What is an inductor?

An Inductor is an electronic component whose main purpose is to provide inductance in electrical and electronic circuits. Inductors are constructed using an inner core material (with high magnetic permeability), and a coil of wire wrapped around this core (as seen in the image below).

An inductor is designed to have a certain amount of inductance which is controlled by manipulating the different variables in the equation for inductance;

• Number of turns of wire of the coil (the more turns, the higher the inductance).
• Coil area 
• Coil length
• Core material permeability (the greater the magnetic permeability of the core material, the greater the inductance). 
• Core material cross-sectional area

The ability of an inductor to provide inductance in circuits has many different applications which include;

• Tuning circuits,
• Choking, 
• Blocking,
• Attenuating and
• Filtering/Smoothing high frequency

Difference between an inductor and inductance

The electrical and electronic world is filled with a plethora of components, devices, terms, units, etc. So things can get confusing fast. One major confusion is the difference between an Inductor and Inductance. As we have just taken a look at inductance and inductors individually, we can look at the differences between them. Inductance defines the property that all conductors have, which is to oppose changes in current. Inductors are components designed to have higher levels of  inductance (compared to a straight piece of wire) and provide inductance in circuits. So, inductance is a property, and inductors are components with a set value of inductance. The amount of inductance that an inductor has can be controlled by varying the number of turns of coil, coil area, coil length, core material cross-sectional area, and core material magnetic permeability.

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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.

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It does this using the energy that is built up within the inductor to slow down and oppose changing current levels.

But, how does an inductor store energy? An Inductor stores magnetic energy in the form of a magnetic field. It converts electrical energy into magnetic energy which is stored within its magnetic field. It is composed of a wire that is coiled around a core and when current flows through the wire, a magnetic field is generated.

This article shall take a deeper look at the theory of how energy is stored in an inductor in the form of a magnetic field. 

Energy, Magnetic fields and Inductors  

Before looking at how an inductor stores energy, we will need to take a couple steps back and learn a little bit about energy.

You might be aware of the phrase; “Energy cannot be created or destroyed, only changed from one form to another.”

This is the first law of Thermodynamics.

The universe has a constant amount of energy that just changes from one form to another. 

Types of energy include;

• Mechanical
• Thermal
• Nuclear
• Chemical
• Electrical
• Magnetic
• Electromagnetic

The main type of energy that we shall be concerned about for this article is Magnetic energy which is found within a Magnetic Field.

How magnetic fields are produced

We have all witnessed the awesome powers of a magnet as it attracts metal objects without the need of physical touch.

But, what exactly gives magnets their awesome abilities?

This comes down to the fact that all matter is made of Atoms which have a nucleus that contains protons and neutrons. 

Orbiting the nucleus on the outside are electrons (which are tiny moving charges).

As these electrons move around the nucleus they create a magnet field around each atom. 

Each atom’s magnet field will have a certain orientation which is known as its Moment. If you were able to look at an object at a subatomic level you would see that every atom resembles a tiny magnet.

However, for an object to be magnetic, it needs to have a large magnetization which is created when all the moments (orientation of an atom) within an object are aligned. 

The majority of objects (like a piece of wood) have their moments misaligned so the net magnetization is zero. 

When the net magnetization of an object is large enough that it creates a substantial magnetic field around it and can be considered to be magnetic. 

How magnetic fields are generated in a wire

We just saw that all atoms have a magnetic field. 

But, there are other instances where a magnetic field can be generated. 

A magnetic field is generated around a wire when a current flows through that wire. A circular magnetic field will surround it.

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 makes great use of this as we shall soon learn.

What is an inductor?

Now let’s take a brief look at an Inductor which will further help us understand how it stores energy.

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 and working principle of an 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. 

So how does an inductor work?

As current starts to pass through the inductor, a magnetic field is generated. 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 energy is stored in an inductor

Now that we have learnt about magnetic energy in magnetic fields, magnetic fields around a wire, and a little bit about inductors, we can take a look at how energy is stored in an inductor.

As mentioned earlier, energy is never created or destroyed, just changed from one form to another.

There are some components (such as a resistor), that just dissipate energy (in the form of heat) when current flows through them. 

However, an inductor is a type of passive electronic component that is capable of converting kinetic energy (flow of electrons) and storing it in its magnetic field which is generated. 

When current flows through a wire a magnetic field is generated around that wire. An energy is stored within that magnetic field in the form of magnetic energy.

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.

So how does an inductor store energy?

An inductor stores magnetic energy in the form of a magnetic field. So it converts electrical energy (flow of electrons) into magnetic energy (stored in 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 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

As you can imagine, inductors make use of this fact in how they are constructed. When you wrap a wire in a coil formation, you increase the strength of the magnetic and therefore increase the amount of energy it can store as well. 
To know the exact strength of an inductor’s magnetic field (and how much energy it stores), you will need to use the formula above and know the values of the variables N, I and L.

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It’s main purpose is to oppose a change in current by producing something known as Back EMF.

Inductors have many uses in circuits which include, blocking AC and allowing DC to pass, electronic filters to separate signals of different frequencies, tuning circuits like Radios and televisions etc. 

An inductor is commonly a coil of wire wound around a central core (imagine wrapping a wire around your finger). 

But, can a straight wire act as an inductor? Yes, a straight wire can act as an inductor. This is because any wire that carries a current will produce a resulting magnetic field which will oppose a change in current. 

How effective a straight wire is at being an inductor is a different story which we shall explore in more detail below. 

What causes a straight wire to act like an inductor

To understand why a straight wire can act as an inductor, we will need to understand a few other principles before proceeding. 

Electromagnetism

Electromagnetism is the relationship between electricity and magnetism.

It is one of the biggest breakthroughs in science, mainly in the branch of Physics. 

It studies the electromagnetic forces that are placed on electrically charged particles.  

Without getting into too much detail, the basics of  electromagnetism states that when an electric current passes through a metal conductor, a magnetic field is produced around that conductor. 

The direction of the magnetic field is always perpendicular to the direction of the current. 

The diagram below shows the magnetic field around a straight wire.

Inductor

As mentioned at the start, an Inductor is a passive electrical component whose main purpose is to store energy in the magnetic field and oppose any change in current.

The inductor was created with the knowledge of electromagnetism and how a wire carrying a current can produce a magnetic field. 

It is a wire that is coiled around a central core.

The inductor has one job in an electrical circuit which is to oppose a change in current which is shown mathematically by the formula dI/dt.

It fights this change in current by producing an Electromotive force (EMF) or back EMF.

The strength of this EMF is largely dependent on the Inductance of the coil which is determined by many factors such as the number of turns in the coil (N), the area of the coil (A) and the length of the coil (d).

The formula for the inductance of the coil can be seen below.

This shows us that the inductance of an inductor is the major property we are concerned with. 

Let’s see how a straight wire can act as an inductor. 

So, we see that the more turns a coil has the greater the inductance. 

It might be said that a straight wire has zero turns and therefore zero inductance.

Saying this infers that current in a closed loop circuit (with straight wires) will reach its maximum value instantly.

But, we know that this cannot be true, as there is a finite amount of time it takes current in a circuit to go from zero to its maximum value. 

This time delay is due to the inductance of the wires in the circuit, which shows that straight wires have some inductance and can act as an inductor.

The amount of inductance a straight wire has is governed by the following equation.

Why a straight wire has inductance but is not a very efficient inductor

Now, how effective a straight wire is at being an inductor is a completely different story.

Let’s look at why using a straight wire is not going to be very efficient and a coil of wire with many turns is a better option.

The greater the magnetic field produced by the current through a wire the greater the EMF which will oppose the changes in current making the inductor more effective.

A single wire has a certain amount of inductance which is largely determined by the length of the wire.

But, there it’s not going to be efficient having long lengths of wire to increase the inductance.

Coiling that same single wire, will instantly double its inductance without having to increase the it’s length.

The magnetic field from the first loop will converge with the magnetic field of the second and double in magnitude.

Adding another coil will triple its inductance and so on. 

This can be seen mathematically by the equation of coiled wire as adding more turns (coils) increases the inductance of wire.

Why is the energy stored in an inductor larger than a straight wire?

The greater the magnetic field generated, the more energy will be able to be stored in that magnetic field.

As we saw above, by taking a single wire with a weak magnetic field and coiling it, we instantly increase the strength of its magnetic field. 

Therefore, an inductor (which has many more turns than a single wire) is going to have a greater magnetic field and more storage for energy. 

How can you make a straight wire act less like an inductor?

What if you do not want a lot of inductance in a circuit?

Maybe you want the straight wire to act less like an inductor. Is it possible?

There are ways to reduce the amount of inductance a straight wire has.

Reducing the length of the wire will greatly reduce its inductance as we know the length of a straight wire largely affects its inductance.

Only, have wires as long as you need, do not add any excess.

Other than that, if the straight wire is placed in a way that it has any coils, or is bunched up together, this is going to increase its inductance.

So, ensure that all wires are straight. 

Final thoughts

So, can a straight wire act as an inductor, yes it can.

However, the next question is whether it is going to be a very effective inductor, and the answer is no.

The greater the EMF that an inductor can produce to resist changes in current, the more effective it is.

We achieve this by taking that straight wire and coiling it. 

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