Electric Current - Definition, Types, Applications, FAQs

Electricity is the flow of charge through a material in an electric current, usually expressed in amperes. In current electricity behaviour, its movements are mostly a result of the movement of electrons through a conductor such as a wire. A pressure difference, which can be likened to an electric pressure, initiates this flow as it forces electrons along a path with low resistance. The existence of electrical devices that help in facilitating life atoms’ motion and operation of current technological advancements depends largely on this movement of electrons.

In this article we will discuss the concept of electric current, it is a keystone to different technologies and applications. It represents the movement of electric charges, which are mostly conveyed by a metal’s electrons as a conductor. Over the last ten years of the JEE Main exam (from 2013 to 2023), a total of three questions have been asked on this concept.

What is Electric current?

Electric current is defined as the rate of flow of electric charge through any cross-section.

i.e If a charge flows through an area for time Δt then average electric current through the area is defined as-

i¯=ΔQΔt

The instantaneous current at any time t is given by

i=limΔt→0ΔQΔt=dQdt

If the flow is uniform then the Current

I=Qt

If a current I flows through an area for time t then, the total charge flowing is

Q=∫Idt

What is Electricity?

The term “Electricity” means, the presence of electrical energy, the flow of electrical charges produces a form of energy which is used to run many mechanical devices and have many applications, such a form of energy is called electrical energy or most commonly known as electricity.

Also read -

• NCERT Solutions for Class 11 Physics
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• NCERT Solutions for All Subjects

Direction of Electric current:

Inside any material, such as a copper wire, when there is flow of electrons inside it, electric current flows across the circuit to which it is connected. Since, the flow of electrons has a specific direction in the material and by convention, the direction opposite to that of flow of electrons is the direction of electric current.

In the electrical circuit shown below, the flow of electrons inside material has direction from left to right so, the conventional direction of electric current will be opposite which is from right to left.

NCERT Physics Notes:

• NCERT Notes Class 11th Physics
• NCERT Notes Class 12th Physics
• NCERT Notes For All Subjects

Relation between charge and Electric current:

There is a mathematical relationship between the charge flowing in a region of space and the amount of electric current flowing through it. From the definition, the rate at which the electrical charges flow in a given region of space is called an electric current, so If dQ amount of charge passes through a given region in time dt then electric current is calculated as I=dQ/dt. The letter ‘I’ is used to denote electric current.

Electric Current: SI unit.

According to the mathematical relationship between electric current and electric charge which is I=dQ/dt. the base unit of electric current can be written as Coulomb per seconds as Cs^-1 but the standard name of SI unit electric current is known as “Ampere” named after the famous scientist Andre Ampere.

So, the SI unit of electric current is known as Ampere, denoted by the letter ‘A’.

1Ampere of electric current.

Ampere is the SI unit used for electric current and one ampere is simply the amount of electric current that passes through a region when one coulomb of charge passes in one second.

Types of Electric current.

In physics, there are two kinds of electric current listed:

1. Direct Current
2. Alternating current

Direct Current:

When electric current flows in any electrical circuit only in one direction such that flow of electrical charges is unidirectional, such types of electric current are referred to as Direct current. For example, the flow of electrons is always in one direction in electrical wires, such electric currents are Direct currents often denoted as DC.

Alternating current.

When the magnitude as well as the direction of electric current changes continuously over time but also repeats the same magnitude and direction of electric current over a fixed period of time, these types of electric currents are referred to as Alternating current. The time at which alternating current keeps magnitude and direction the same periodically is known as the time period of alternating current. Alternating current is often denoted as AC.

The most common periodic representation of alternating currents is sine and cosine waves, as shown in the diagram below.

Also read :

• NCERT solutions for Class 12 Physics Chapter 3 Current Electricity
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Relationship between Electric current and Voltage.

In electricity, the fundamental law which gives the relation between electric current, Voltage applied is given by Ohm’s law. Ohm’s law state that if the voltage applied across a conductor is V and electric current flows across the conductor are I then the ratio, V/I=R is constant, and this constant ‘R’ is known as the resistance of the conductor. Resistance is simply the ability of a material to oppose the flow of electrons inside the material.

Applications of Electric current:

Some of the common uses of electric current in everyday life as well as in scientific fields are listed as:

1. Electric current is used to run many devices such as refrigerators, electric fans and many household items.
2. Electricity is used as electrical energy and converted into light energy such as electric bulbs and mechanical energy such as electric motors.
3. Almost all the appliances in industries such as computers, electronic and communication fields such as antennas, mobile phones all these kinds of appliances work on electricity.
4. Our daily life such as public transport systems, personal computers, water heaters all works on electricity.

Hence, electricity is the basis of our day to day necessities.

Properties of Electric Current

• Current can be added algebraically.

• Current is a tensor quantity ( if in options tensor is not given take current as scalar quantity)

• Unit of Electric Current: The unit of electric current is Ampere or A.

The current is said to be 1 ampere when 1 coulomb of charge flows through any cross-section in every second.

Calculating Current in Different Situations

1. When the charge is performing translatory motion

• If n particles each having charge q pass a given area in time t

i=nqt

2. When the charge is performing rotatory motion

If a point charge q is moving in a circle of radius r With Velocity V (frequency , angular speed and time period T).Then,

i=qt⇒qT=qν=qV2πr=qw2π

Types of Current

1. Alternating current

• Magnitude and direction both vary with time.

• Shows a heating effect only.

• Its symbol

2. Direct current

• No change in magnitude and direction with time.

• Shows the heating effect, chemical effect and magnetic effect of current.

• It's a symbol

Current Independent of Area

Current does not change with change in cross-sectional area

Here i1=i2=i3

Solved Examples Based on Electric Current

Example 1: One billion electrons pass from A to B in 1 ms. What is the direction and magnitude of the current?

1) 1.6 A

2) 0.8 mA

3) 0.16 A

4) 1.6 mA

Solution:

Translatory motion of charge

i=n q A

wherein

If n particles charge q pass per second per unit area, the current associated with a cross-section area A is:

i=Net=(109)(1.6∗10−19C)10−3=1.6∗10−7 A
i = 0.16 m A.

The current flows from B to A.

Hence, the answer is the option (3).

Example 2: The average value of a sinusoidal A.C. current over one cycle is:

1) Positive

2) Negative

3) Zero

4) Can be positive negative or zero.

Solution:

Alternating current

magnitude and direction both vary with time

wherein

The average of sinusoidal A.C. current over one cycle is zero.

Hence, the answer is option (3).

Example 3: Alternating current can

1) produce a heating effect

2) Be used for Charging of battery

3) can be used for electrolysis

4) All of the above

Solution:

Alternating current

Shows a heating effect only.

A.C. current cannot be used for electrolysis or battery charging as its average value is zero.

Hence, the answer is the option (1).

Example 4: Direct current has

1) Both magnitude and direction constant

2) only magnitude constant

3) only direction constant

4) None of the above

Solution:

Direct current

No change in magnitude and direction with time.

wherein

Direct current has their direction constant. i.e it cannot reverse its direction.

Hence, the answer is option (3).

Example 5: Which of the following effects can be shown by both direct current and alternating current?

1) Magnetic effect

2) heating effect

3) Chemical effect

4) Charging of battery

Solution:

Alternating current Shows a heating effect only.

But direct current Shows the heating effect, chemical effect and magnetic effect of current.

Hence, the answer is the option (2).

Summary

Electric current is defined as the movement of electric charge through a medium, typically carried by electrons that move along a conductor such as a cable and in current electricity, which generates energy that can be useful in powering certain circuits and devices up. This energy is made possible by the flow of current. Current strength is the measure of the amount of charged particles that are passing by the unit of time in a particular section of a wire.or generator.