Electricity and Magnetism
A complete physics website covering electric current, Ohm’s law, resistance, electric power, series and parallel circuits, magnetism, electromagnetism, magnetic fields, electromagnetic induction, motors, generators, diagrams, formulas, solved examples, and exercises.
1. Electricity
Electricity is the flow of electric charge through a conductor.
2. Ohm’s Law
The current flowing through a conductor is directly proportional to the potential difference across it, provided temperature remains constant.
| Symbol | Meaning |
|---|---|
| V | Voltage |
| I | Current |
| R | Resistance |
Example
Find current if voltage is 12 V and resistance is 4 Ω.
I = 12/4
I = 3 A
3. Series and Parallel Circuits
Series Circuit
Parallel Circuit
4. Electric Power
Electric power is the rate of consumption of electrical energy.
Solved Problem
Find electric power if V = 220 V and I = 2 A.
P = 220 × 2
P = 440 W
5. Magnetism
A magnet is a material that attracts iron, cobalt, and nickel.
Properties of Magnet
- Like poles repel.
- Unlike poles attract.
- A freely suspended magnet points north-south.
6. Electromagnetism
Magnetic field produced due to electric current is called electromagnetism.
Applications
- Electric bell
- Cranes
- Speakers
7. Electromagnetic Induction
The production of induced current in a conductor due to changing magnetic field is called electromagnetic induction.
Applications
- Electric generator
- Transformer
- Induction cooker
8. Practice Exercises
Short Questions
- Define electric current.
- State Ohm’s law.
- Define resistance.
- What is magnetism?
- Define electromagnetic induction.
Numerical Problems
- Find current if V = 24 V and R = 6 Ω.
- Calculate power if V = 110 V and I = 5 A.
- Find equivalent resistance of 2 Ω and 4 Ω connected in series.
9. Formula Summary
| Topic | Formula |
|---|---|
| Current | I = Q/t |
| Ohm’s Law | V = IR |
| Electric Power | P = VI |
| Series Resistance | R = R₁ + R₂ + R₃ |