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JEE Main Current Electricity Revision Notes

## JEE Main Current Electricity Revision Notes - PDF Download

The definition of electric current is the rate of flow of electric charge over any plane of a wire. This flow of charge is also referred to as the electric current flowing through a wire.

I = Electric current = q / t

A = SI unit of electric current is Ampere.

The electric current’s conventional direction is the course of motion of positive charge.

Consider that a charge (q) rotates in a loop having a frequency (f),

Then the equivalent current, i = q * f

## Current Electricity Notes JEE

Some important current electricity JEE notes are given below.

### Types of Electric Current

The electric current can be classified into the following two types.

Direct Current (DC)

In direct current, the magnitude and direction of current do not alter with time. For example, cells, batteries, or DC dynamos operate on direct current.

Alternating Current (AC)

Alternating Current can be explained as the current whose value fluctuates incessantly and there is a periodical fluctuation of its direction. For example, an AC dynamo operates on alternating current.

Current Density

Current density can be defined as the electric current flowing through per unit area of the cross-section of a wire.

J = Current density = I/A.

The S.I. unit of current density = ampere metre-2.

Dimensional formula = [AT-2].

### Current Electricity JEE Main Notes

Ohm’s law is another important topic that is discussed below in the current electricity notes for JEE Main.

Ohm’s Law

At constant temperature, the electric current ‘I’ passing through a conductor is directly proportional to the potential difference V induced across its ends.

Mathematically, I ∝ V,

Or, V = IR.

Here,

R = The electrical resistance of the conductor.

Electrical Resistance

Electrical resistance is a kind of obstacle provided by any conductor in the track of the flow of current.

R = Electrical resistance = V/I

The S.I. unit of resistance= ohm (Ω)

Dimensional formula = [ML2T-3A-2]

R = Electrical resistance of a conductor = ρ * l / A

Here,

l = length of the conductor

A = area of cross-section

ρ = a conductor’s resistivity

### Solved Current Electricity Examples

Some solved examples from the current electricity IIT JEE notes are given below.

Q1. From scientific experiments, lightning is the most powerful natural current. From the lightning, consider that 109 J energy moves to the potential difference of 5 × 107 V by taking a time-interval of 0.2 s. Then, calculate the amount of charge, current, and power generated by the lightning.

Ans: Energy transferred U = 109 K

Voltage V = 5 x 107 V

Time t = 0.2 S

Charge q =?

Current I =?

Power delivered in 2s =?

So, the solution is

U = qV

q = U / V = 109 / 5 x 107 = 20 C…. Ans [1]

q = 20 C

Again, I = q / t = 20 / 0.2 = 100 A …. Ans [2]

Then, P = VI

P = 5 * 107 * 102 = 5 x 109 W

P = 5 GW…. Ans [3].

Q2. An aluminum wire has a 10-6 m2 area of cross-section. This conductor supplies a current of 2 A. Let’s consider that the number of electrons per cubic meter is 8 × 1028. Then, compute the current density and average drift velocity.

Ans: Given data,

A = 10-6 m2

I = 2A

N = 8 × 1028

We need to calculate, J =?

Vd = ?

So, J = I / A = 2 / 10-6 = 2 * 106 Am-2……... Ans [1].

J = neVd

\[V_{d} = \frac{J}{ne} = \frac{2 \times 10^{6}}{8 \times 10^{28} \times 1.6 \times 10^{-19}}\]

\[= \frac{10^{6}}{64 \times 10^{8}} = \frac{10^{-2}}{64} = \frac{100}{6} \times 10^{-4} m/s\]

Vd = 1.56 * 10-4 m/s…… Ans [2].

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Q1. What do you Mean by Superconductors?

Ans: We can call a material as a superconductor when we recognize that a set of physical properties are found in this material where electrical resistance disappears, and magnetic flux fields are excluded from the material. Any material exhibiting these properties is a superconductor.

Q2. Define the Meissner Effect and State who Discovered it?

Ans: Meissner effect can be explained as the dismissal of the magnetic field a super-conductor when it has its transformation to the higher end of the superconducting stage. It was discovered by Walther Meissner and Robert Ochsenfeld in 1933.

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