JEE Physics Notes: Current Electricity

Introduction to Current Electricity

Current electricity deals with the movement of electric charges in a conductor. This chapter covers concepts such as electric current, resistance, Ohm’s law, and various electrical circuits.

Electric Current

Electric current is the flow of electric charge through a conductor. It is given by:

I = Q/t

where I is the current, Q is the charge, and t is the time.

Types of Current

• Direct Current (DC): Flows in one direction.
• Alternating Current (AC): Changes direction periodically.

Ohm’s Law

Ohm’s law states that the current flowing through a conductor is directly proportional to the voltage applied across it and inversely proportional to its resistance.

V = IR

where V is the voltage, I is the current, and R is the resistance.

Electrical Resistance

Resistance opposes the flow of current and is given by:

R = ρ (L/A)

where ρ is the resistivity, L is the length, and A is the cross-sectional area of the conductor.

Factors Affecting Resistance

• Material of the conductor
• Length of the conductor
• Cross-sectional area
• Temperature

Series and Parallel Circuits

Resistance in Series

For resistors in series, the total resistance is given by:

Rtotal = R1 + R2 + R3 + ...

Resistance in Parallel

For resistors in parallel, the total resistance is given by:

1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ...

Kirchhoff’s Laws

Kirchhoff’s Current Law (KCL)

The sum of currents entering a junction is equal to the sum of currents leaving the junction.

ΣIin = ΣIout

Kirchhoff’s Voltage Law (KVL)

The sum of all voltages around a closed loop is zero.

ΣV = 0

Electrical Power and Energy

The power consumed in a circuit is given by:

P = VI = I²R = V²/R

The electrical energy is:

E = Pt

Applications of Current Electricity

• Electric circuits and household wiring
• Battery-operated devices
• Power transmission and distribution
• Electronic components and circuits

This chapter is crucial for solving JEE Physics problems related to electric circuits, resistances, and network theorems.