📘Class 10 Science – Chapter: Magnetic Effects of Electric Current Notes

🔌 Magnetic Field and Field Lines 

• Magnetic field strength is measured in tesla (T).

• The magnetic field gets weaker as we move away from the magnet.

• Earth itself acts as a giant magnet; its magnetic field protects us from cosmic radiation.

Important Example:
If a compass is placed near a bar magnet, the needle aligns along the magnetic field direction.

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🔦 Electromagnetism and Force on a Current-Carrying Conductor

• Electromagnetic force arises due to interaction between magnetic field and current.

• Maximum force is when the current is perpendicular to the magnetic field.

Formula for Force (F):
F = B × I × L × sinθ
Where,

• F = Force on conductor

• B = Magnetic field strength

• I = Current

• L = Length of conductor in the field

• θ = Angle between B and I

Applications:

• Electric bell

• Magnetic cranes in junkyards

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🏒 Electric Motor

• DC motor uses direct current and is commonly used in toys and household appliances.

• AC motor is used in industries and runs on alternating current.

Detailed Working:

1. When current flows through the rectangular coil placed in a magnetic field, the two arms of the coil experience opposite forces.

2. This creates a torque which rotates the coil.

3. The commutator reverses the current after every half rotation to keep the direction of rotation the same.

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⚡ Electromagnetic Induction

• Induced current depends on:

  • Strength of magnetic field

  • Speed of motion

  • Number of turns in coil

Applications:

• Electric generator

• Induction stove

• Transformers

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🔋 Electric Generator

AC Generator Working Steps:

1. Coil is rotated in magnetic field.

2. Magnetic flux through coil changes.

3. Induced current is produced (changes direction every half cycle).

DC Generator:

• Same working, but commutator (split ring) ensures current flows in one direction.

Example:
Used in power stations to generate electricity.

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📃 Domestic Electric Circuits

Household Wiring System:

• Generally uses parallel combination of devices.

• This ensures:

  • Equal voltage supply to all devices

  • Independent operation of devices

Precautions:

• Never use damaged wires or overload circuits.

• Always install earth wire for metallic appliances like geysers.

Difference between Fuse and MCB:

Feature	Fuse	MCB
Mechanism	Melts on overheating	Switches off automatically
Reusability	One-time use	Can be reset and reused
Accuracy	Less precise	More sensitive to current