Magnetic Effects of Electric Current

Notes

1. Magnet and Magnetic Field

Magnet

A magnet is a material that attracts iron, nickel and cobalt.

Properties

Has two poles: North (N) and South (S)

Like poles repel each other.

Unlike poles attract each other.

Magnetic poles always exist in pairs.

Magnetic Field

The region around a magnet where its magnetic force can be experienced is called the magnetic field.

Magnetic Field Lines

Magnetic field lines are imaginary lines representing the magnetic field.

Characteristics

Originate from North pole.

End at South pole.

Never intersect.

Closer lines indicate stronger magnetic field.

Parallel equally spaced lines indicate uniform magnetic field.

Board Diagram

N ---------> S

)))))))))))))))

))))))))))))))))

2. Magnetic Field Due to Current Carrying Conductor

In 1820, Hans Christian Oersted discovered that electric current produces a magnetic field.

Straight Conductor

Magnetic field lines are concentric circles around the conductor.

⊙ Current coming out

○ ○ ○ ○ ○

⊙

○ ○ ○ ○ ○

Right-Hand Thumb Rule

If the right thumb points in the direction of current, the curled fingers show the direction of magnetic field.

Remember: Thumb → Current

Fingers → Magnetic field

Frequently Asked in Boards

Factors Affecting Magnetic Field Strength

Current through conductor

Distance from conductor

Higher current = Stronger magnetic field

3. Magnetic Field Due to Circular Loop

Field lines become stronger near the centre.

Increasing

Current

Number of turns

increases magnetic field.

4. Solenoid

A long cylindrical coil having many turns of insulated copper wire is called a solenoid.

Properties

Produces magnetic field similar to bar magnet.

Field inside solenoid is uniform.

Strong magnetic field.

Diagram

N ((((((((((((((((( S

Electromagnet

An electromagnet is a temporary magnet produced by passing current through a solenoid wound over a soft iron core.

Uses

Electric bell

Cranes

Relays

Motors

Difference

Electromagnet Permanent Magnet

Temporary Permanent

Strength adjustable Fixed

Current required No current

5. Force on a Current Carrying Conductor

When a conductor carrying current is placed inside a magnetic…