Current Electricity - Student Guide

⚡ Current Electricity

📘 What is Current Electricity?

Current electricity is the flow of electric charge through a conductor (like a wire). It is caused by a difference in electric potential (voltage) across the conductor.

The flow of charges (usually electrons) creates electric current. This concept is the foundation of all electrical and electronic devices.

📚 Core Concepts

1. Electric Current (I)

Electric current is the rate of flow of electric charge.

I = Q / t

Where:

  • I = current (amperes)
  • Q = charge (coulombs)
  • t = time (seconds)

2. Ohm’s Law

Ohm’s Law gives the relationship between voltage (V), current (I), and resistance (R).

V = I × R

3. Resistance (R)

Resistance is the opposition offered by a material to the flow of current.

R = ρ × (L / A)

Where:

  • ρ = resistivity of the material
  • L = length of the conductor
  • A = cross-sectional area

4. Electric Power (P)

Power is the rate at which electrical energy is consumed or produced.

P = V × I = I² × R = V² / R

5. EMF and Potential Difference

EMF (Electromotive Force): The total energy supplied by the source per coulomb of charge.
Potential Difference: The energy used by the charge to do work between two points.

📌 Important Equations Summary

I = Q / t
V = I × R
R = ρ × (L / A)
P = V × I = I² × R = V² / R
Energy = Power × Time = V × I × t

💡 Daily Life Examples of Current Electricity

  • Mobile Charging: Electricity flows from the charger to your phone’s battery.
  • Electric Bulbs: Current heats the filament to produce light.
  • Electric Vehicles: Batteries supply current to motors for movement.
  • Computers & Laptops: Work using controlled flow of current through circuits.
  • Heaters & Geysers: Convert electrical energy to heat using resistance.
Example: When you switch on a fan, the electrical current flows from the power supply to the motor of the fan, which causes it to rotate.

✅ Summary for Quick Revision

  • Electric current is the flow of charges, measured in amperes.
  • Ohm’s Law: V = I × R is a key relationship.
  • Resistance depends on material, length, and thickness.
  • Power tells how fast electrical energy is used.
  • Current electricity is used in all modern devices and machines.
💡 Tip: Remember — High resistance means less current flow, and low resistance allows more current to pass!
current electricity