Electric Current in Conductors

What is an Electrical Conductor?

Electrical conductors are the material that allows the free flow of electrons through them. This means they allow electrical current to pass through them. Electrical conductors are generally made up of copper, aluminum, and their alloys. The electrical charges in an electric conductor move from atom to atom as the potential difference is applied through them. Mostly the electric conductor is used in the form of wire. The electrical conductor used to transfer electricity is normally stranded. Compared to a single wire of the same cross-section area, stranded conductors have great flexibility and mechanical power. In this article, you will learn what makes an electric current flow in a wire.


Insulators

Insulators are the material that resists the free flow of electrons from one atom/molecule to another. For example, if you transfer charge at a particular location on an insulator, it will remain at the same place while in case of the conductor it gets distributed evenly. Due to the above reasons, they are not used for the transfer of charges or say current. But due to this property, they are used for several purposes like in electrostatic experiments and demonstrations. Some examples of insulators include paper, plastics, rubber, dry air, Styrofoam, and glass.


What is Current?

When we apply a potential difference across any material, a flow of electrons (charges) takes place. The rate of flow of this electron is called current. If the material on which the potential difference is applied is a conductor, then we say this current to be the current in the conductor. If Q amount of charge flows through any cross-section of a conductor in time t, then- the current is defined as the rate of the flow of electrons, i.e

I = Q/t

The SI unit of the current is Ampere (A).

The current is mostly divided into two groups, i.e. alternating current and direct current, depending on the electric charge flow. In direct current, the charges flow through unidirectional while the charges flow in both directions in alternating current.


The Direction of the Current

As per the electron theory, when the potential difference is applied across any conductor in a circuit, some matter flows into it that actually constitutes the flow of current. It is believed that the matter flows from high potential to a lower potential, i.e from the positive terminal to the negative terminal of the battery. Since the current is having the direction, so technically it should be a vector quantity because it has both the direction and value but in reality, it is a scalar quantity. 


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Thus, conventionally the direction of current flow is from the positive terminal to the negative terminal of the battery.  


Current in the Conductor

We all know that conductors are the substances that allow current to pass through them. When the conductor is not connected to the battery, the free electrons tend to move freely here and there. This electron moves randomly inside the conductor with a certain velocity. This velocity is called thermal velocity. Since the whole motion is random, the average velocity equals zero. 


Next, the external electric field is applied. Once the battery is applied to the conductor, the electron starts moving towards the positive terminal of the battery. As the electrons move towards the positive terminal of the battery, it gets accelerated.  Since the electron is moving in only one direction, it gets collided with the positive ions as well. With this collision, electrons tend to lose their velocity which they had gained because of the acceleration. Whenever any charged particle goes into any conductor, it doesn’t move into a straight line, it collides with the other charged particle. Because of this loss, a very small increase in velocity takes place. The average of this small gain in the velocity is called the Drift velocity. Drift velocity can be defined as the average of the velocity gained in a material due to an electric field.

V = I/nAq

Where,

v - Drift velocity

I - Electric current

n - no of electrons

A - Area of the cross-section of the conductor

q - charge of an electron in coulombs


Mobility of an Electron

The mobility of an electron is defined as the drift velocity of an electron for a unit electric field. The mobility depends upon the potential difference applied, conductor length, the density of charge carriers, current and area of the cross-section of the conductor. 

μ = Vd/E

Where, μ = mobility of an electron

Vd = Drift velocity of an electron

  E =  Electric field applied


Fun Facts

  • Electricity travels an hourly distance of 6,696,000 miles.

  • Coal is the world's largest energy source for generating electricity.

  • A static electricity spark can measure up to 3,000 volts.

  • Electric fields act in a manner similar to gravity. Whereas gravity attracts always, electrical fields can either attract or repel.

FAQ (Frequently Asked Questions)

1. Why are Copper and Aluminum Wires Usually Used for the Transmission of Electricity?

Ans. Usually, copper and aluminum wires are used for electricity transmission because they have very low resistivity and because of low resistivity, it decreases the resistance thereby increasing the amount of current flowing through the conductor, making them good electricity conductors. Hence,  aluminum and copper wires are generally used for electricity transmission.

2. Explain How Electric Current is Developed in a Conductor?

Ans. Conductors have plenty of free electrons that move in random directions when it is not connected to any external electricity source. When a conductor's ends are attached to an external source of electricity, then an electrical force acts on the conductor's electrons, and the electrons (negative charged) start traveling from the negative end to the conductor's positive end. This movement of electrons constitutes the conductor's electrical current. This is how a conductor produces current.