What Is An Amperes?: A Basic Electrical Unit

Do you require information on Amperes? Then, read through this article on “What Is An Ampere” to get the information you require.

This article is equipped with every information you require. Therefore, I recommend that you read it till the end.

To ease your reading, I will begin with an overview. This will be immediately followed by the factors affecting current flow in a conductor.

Besides, in the second section, I will discuss the resistivity of a conductor. This then leads to the comparison between conductors, semiconductors, and insulators.

I will also be focusing on their effect on current flow.

Furthermore, we will see the current flow’s effects on a conductor. Then, the force on a current-carrying conductor. Ampere’s Law will immediately follow this.

Lastly, I will give answers to some frequently asked questions.

What Is An Ampere; Overview

What Is An Ampere; Overview

The Ampere is the SI unit for current in a conductor. It measures the rate at which current flows through a conductor.

Before now, ampere was referred to as the constant that produces a force between two conductors. However, these conductors must be straight and parallel to each other.

More so, they should have infinite length. Furthermore, these conductors of a negligible cross-section.

Also, they should be placed 1m apart in a vacuum. Hence, they will produce a force equal to 2×10−7 newton per meter length.

In 2019, ampere was given a redefinition during the General Conference On Weights and Measures.

In the new definition, Ampere is defined by taking a fixed number. This number is an elementary charge of 1.602176634×10−19 coulomb.

This apparently contradicts the initial work of Andre-Marie Ampere. He described ampere as a representation of a flow of one coulomb of charges per second.

That is, 1 ampere = 1 coulomb/second (1A = 1C/1s).

By comparing Ohms Law, a circuit with a potential difference of 1 volt and resistance of 1 ohm will produce a current of 1 ampere.

The definition of ampere by Andre-Marie Ampere was a result of his experimental discovery.

However, the experiment led him to discover the force of a current-carrying conductor.

Even so, he saw that a wire carrying electric current can attract or repel another wire next to it that is also carrying current.

Though the attraction is magnetic, no is necessary for the effect.

Lastly, his experiment led him to give the perfect definition of the current of his time.

In his honor, the SI unit of current is named after him.

Other units used to measure current are – milliamperes (mA), microampere (uA), and nano amperes (nA). It is scarce to hear kiloamperes (kA).

Factors Affecting Current Flow In A Conductor

Factors Affecting Current Flow In A Conductor

The flow of current through a conductor is affected majorly by five factors.

However, one of the factors has to do with the current source, while the other four focus on the resistance of the conductor.

Furthermore, the resistance of a conductor is due to the collisions of charges. Current flow has to do with the movement of charges.

These charges collide and give rise to resistance.

Thus, the primary factors that affect the flow of current in a conductor are:

Voltage Across The Conductor

One factor that affects current flow through a conductor is the potential difference (voltage) across the conductor.

The voltage is the driving force that causes a current to flow through a circuit.

According to Georg Simon Ohm, the current in a circuit increases as the voltage increases.

However, all other physical quantities remain constant. This is called Ohm Law.

Length Of The Conductor

The length of a conductor also plays a vital role in the current passing through the conduct. This affects the resistance of the conductor.

Naturally, every electric conductor has resistance without connecting a resistor. This resistance comes with the impurities that allow the conductor to conduct.

In other words, infinite current flow in a conductor without resistance. Thus, if resistance is zero, the current will be equal to infinity.

Anyways, such a conductor does not exist. Because the impurities in the conductor are what allow it to conduct.

As such, there are bound to be collisions along the conductor.

Hence, from the above explanation, a longer conductor allows more collisions. Thus, increasing the resistance.

By implication, a conductor’s resistance increases as the conductor’s length increases. That is, resistance is directly proportional to length.

That is, R ∝ L…………(i).

Cross-sectional Area Of The Conductor

The wider the cross-sectional area of a conductor, the lesser the resistance of that conductor.

In other words, the resistance of a wire is inversely proportional to the cross-sectional area of that same conductor.

For instance, a larger pipe will allow the water to flow at a higher rate.

However, you will have a lesser rate of water flow through a narrow pipe. Thus, the wider pipe has less resistance to water flow.

Consequently, the wider the cross-sectional area of a conductor, the higher the flow of electrical current.

Hence, the cross-sectional area varies inversely to the resistance.

That is, R ∝ 1/A……………(ii).

Temperature Of The Conductor

When current passes through a conductor, it produces heat. In other words, the temperature of that conductor increases.

This temperature rise energizes the electrons.

In addition, the ions vibrate more vigorously. Hence, increasing the collisions between free electrons and ions in the conductor.

This is applicable in the filament of a bulb and a PTC thermistor.

Therefore, the resistance of a conductor increases with the temperature rise. Thus, reducing the flow of current.

Materials Used In Making The Conductor

Another factor that affects the flow of current is the material the conductor is made of. Various materials have different conducting abilities.

In other words, some materials are better conductors than others. Thus, they offer a higher flow of electrical charges than others.

However, silver is seen to be one of the best conducting materials.

Nevertheless, due to its high cost, it is not useful in a household electric circuit.

Nevertheless, copper and aluminum are less expensive but have a high conducting ability. Hence, they are mostly used in household circuits.

Although, their conducting ability is not as high as that of silver.


If we bring expression (1) and expression (2) together,

R ∝ L/A…………(iii).

Equating expression (3),

R = P * L/A.

Therefore, P = R * A/L.


R = Resistance of the conductor.

L = Length of the conductor.

A = Cross-sectional area of the conductor.

P is a constant of variation called Resistivity.

Resistivity Of A Conductor

Resistivity Of A Conductor

The resistivity of a conductor is the resistance the material offers per unit length of the cross-sectional area.

This resistivity is a property of the material used in producing the conductor. It depends on temperature and pressure.

However, resistivity is used to compare the ability of a material to conduct current. Hence, conductors have low resistivity.

On the other hand, insulators have very high resistivity.

The SI unit of resistivity of a conductor is ohm-meter. Its reciprocal is conductivity.

Furthermore, the table below shows the resistivity of some conducting materials.

MaterialResistivity (ohm-meter)
Silver1.59 x 10-8
Copper1.7 x 10-8
Gold2.2 x 10-8
Aluminum2.8 x 10-8
Tungsten5.6 x 10-8
Iron10 x 10-8
Platinum11 x 10-8
Lead22 x 10-8
Nichrome150 x 10-8
Carbon3.5 x 10-5

Conductivity Of A Conductor

Electrical conductivity is the measure of the easy flow of electric charge through a material. It is the reciprocal of resistivity.

Even so, it is denoted by the symbol δ. Its SI unit is siemens per meter (S/m).


δ = 1/p.

Therefore, δ = L/(R*A).

However, conductors give very little resistance to the flow of electric current.

Materials are classified as conductors, semiconductors, and insulators.

Hence, the conductivity of conductors is higher than that of semiconductors and insulators.

Conductors, Semiconductors, And Insulators

Conductors, Semiconductors, And Insulators


A conductor is a material that allows electric energy and thermal energy to pass through it. It has a very low resistance and high conductance. Most conductors are metals.


Semiconductors are materials that can act as an insulator in some conditions and can also act as a conductor. They are mainly products of silicon, germanium, and gallium arsenide.

Types Of Semiconductors

Semiconductors are classified into intrinsic and extrinsic semiconductors.

Intrinsic Semiconductors

The intrinsic type semiconductor is known to be a chemically pure semiconductor.

It has very few charge carriers (holes and electrons). Hence, its conductivity is low.

The holes and electrons it possesses are of equal quantities. As a result, its resistivity is high.

Extrinsic Semiconductors

An extrinsic semiconductor is a semiconductor to which a small amount of impurity is added.

It is an intrinsic semiconductor that has gone through a process called doping.

Extrinsic semiconductors have a higher conductivity compared to intrinsic semiconductors.

Doping is the process of adding impurities to an intrinsic semiconductor to improve its conductivity.

This process of doping produces two types of semiconductors. These are N-type and P-type semiconductors.

N-type Semiconductor

The N-type semiconductor is a semiconductor that has a greater number of electrons than holes. To have an N-type semiconductor, you dope it with pentavalent impurities.

These pentavalent impurities are impurities with 5 valence electrons. More so, they produce N-type semiconductors by adding extra electrons to them.

P-type Semiconductor

The P-type semiconductor is produced by adding trivalent impurities to an intrinsic semiconductor. Furthermore, they have a greater number of holes than electrons.

Even so, trivalent impurities have 3 valence electrons. Therefore, they produce P-type semiconductors by producing holes or electron deficiencies.


Insulators are materials that do not allow an electric current or heat to flow through them. They have infinite resistance.

In other words, their resistivity is high and conductivity is almost zero.

However, this material can not be doped.

Effect Of Current Flow On A Conductor

When current flow on a conductor, certain effects and changes occur on the conductor. These include:

Rise In Temperature Of The Conductor

When current passes through a conductor, the heating effect occurs due to the resistance of the conductor.

This leads to power loss and a rise in the temperature of the conductor.

However, the temperature returns to normal when the current stops flowing through the conductor.

Increase In Length Of The Conductor

The flow of current through a conductor causes a rise in temperature. During this temperature rise, the molecules gain kinetic energy.

As such, try to break the bond that holds them together.

As a result, the conductor expands. When the current stops flowing, the length of the conductor tends to return to its original size.

However, due to the vibration and displacement of these molecules, they do not get their actual original size.

Therefore, there is a little increase in the length of the conductor.

This increase is not always obvious at the first instant but with a continuous flow of current through the conductor with time.

After a long period, you will notice a sag on the conductor (in power transmission and distribution lines).

Hence, this could lead to short circuit fault, open circuit, weak cable joint, and so on.

Magnetic Force Around The Conductor

A magnetic effect is experienced when current flows through a conductor. This effect is due to the magnetic field that exists around the conductor when current flows through it.

Hence, it is called an electromagnetic field.

The next section discusses this in detail.

Force On A Current Carrying Conductor

As electric current flows through a conductor, it creates a magnetic field. This magnetic field is such that it can exert a force on a magnet placed close to it.

However, the force exerted by the current-carrying conductor on the magnet could be attractive or repulsive.

The force is due to the magnetic field around the conductor.

More so, the direction of the current determines whether it will attract the magnet or repel it. Again, this is easier to understand with an experiment.


F = B * I * L.


F = the force on the conductor.

B = the magnetic flux density (measured in Telsa).

I = the current flowing through the conductor.

L = the length of the conductor.

Also, if two parallel current-carrying conductors are placed close to each other, they will be an interaction. This interaction comes between their magnetic fields.

As a result, a force will act between the conductors (wires).

The force acting on the conductor could either be attractive or repulsive. Thus, it depends on the direction of the current flow on each conductor.

Ampere’s Law

Ampere's Law

Ampere’s law states that “with a constant permeability of free space, the magnetic field created by an electric current is directly proportional to the magnitude of the electric current flowing through the conductor”.

The field created by a straight current-carrying conductor form concentric circles. However, the field gets weaker as it moves away from the conductor.

Pros And Cons


  • It is the standard unit for current.
  • Also, it is one of the parameters that determine electrical power.
  • Even so, it helps to compute the electrical energy for a building.


  • It could be dangerous when wrongly handled.

What Is An Ampere; Frequently Asked Questions

Frequently Asked Questions
1. What is an ampere easy definition?

It is a unit measure of electron flow rate in a conductor. You can also refer to it as the rate of current flow. However, 1 ampere of current equals 1 coulomb of electrical charge (6.24 x 1018 charge carriers).

2. What is an ampere equal to?

An ampere equals a charge of one coulomb per charge.

3. What is the difference between voltage and ampere?

Voltage is a measure of the pressure that drives electron flow. On the other hand, amperage is a measure of electron flow.

4. How many watts are in an amp?

Voltage = 120V.
Current = 1A.
Power = 120 * 1 = 120W.
If the voltage is 220V, then you will have 220W.

5. What is meant by 5 amperes?

Ampere is an electrical current rating. For instance, if a fuse is rated at 5 amps, it means a current above 5 amps can not flow through it.
In other words, the fuse will melt and break the circuit if a current above 5 amps flow through it.

6. Why the unit of current is ampere?

It is named after Andre-Marie Ampere. He is the one that gave the definition of current. Hence, one of the pioneers in electrical science.

7. What is the difference between watt and amp?

Amperes is the measure of the flow of electric charges. While Watts is the working capacity of an electrical circuit. It is the product of volts and amps.

8. How do I convert volts to amps?

For you to do this, you need a fixed wattage. However, you use the formula below to convert volts to amps with a fixed wattage.
amps = watts / volts.

9. What kills voltage or current?

Voltage does not kill. It only drives the current. It is current that is responsible for electrocution. Note that both DC and AC voltages and currents are hazardous.

10. What is a live wire called?

Basically, there are 3 wires in a cable. The live, neutral, and earth wires.
Furthermore, the live wire is the wire with high potential.
It delivers current to the load. On the other hand, the neutral wire is a return path for the current.
While the earth wire earths the installation.

What Is An Ampere; Wrap Up

What Is An Ampere; Wrap Up

Ampere is the standard unit of measuring current.

It is the standard way of quantifying the flow of current in an electric circuit.

Also, it is driven by volts.

However, the flow of current can be affected by certain factors that are inevitable.

Therefore, you can only try to control them when necessary.

Current flow on the other hand is easy with conductors. With insulators, current can not flow.

Nevertheless, semiconductors can allow a certain amount of current to flow through them without damage.

Furthermore, current-carrying conductors create electromagnetic fields around themselves. These fields are concentric in nature.

Hence, this article has every information you require on amperes.

It gives every detail of Andre-Marie Ampere’s work on current. Even so, it contains every mathematical expression that accompanies it.

Discussing the effect of current on a conductor explains the reason for sag and weak joints. Thus, you have been well informed.

I hope this article is found useful.

Therefore, fill out the “Leave A Reply” form to share your thoughts.

Moreover, you may want to read other articles like this, please visit the following articles:

What Does Current Mean

Alternating Current (AC)

What Is An Atom?

Christian Jerome
Akan Christian writes for PowerVersity.com. He holds an HND in Electrical/Electronic Engineering. Christian enjoys reading, listening to solemn music, singing, and playing sports. For PowerVersity.com, Christian writes reviews, buying guides, and best pick articles.


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