FORM 2 CHAPTER 7 (Electromagnet)

Electromagnet

1. An electromagnet is a type of magnet that has
temporary magnetic effect when electric current flow
through it.

Electromagnet

electromagnet

Electricity source

Conductor (solenoid)

https://www.youtube.com/watch?v=na_FpTXLFa8

Solenoid

 A cylindrical coil of wire acting as a
magnet when carrying electric
current.

 Solenoid has stronger magnetic field
compare to straight wire.

Electric Bell

1.

Electric bell : https://www.youtube.com/watch?v=nygn7wB7658

Electric Bell

2.When switch is pressed, the circuit is complete, the solenoid
(coil of wire) becomes an electromagnet and attracts the iron.

iron

Electric bell : https://www.youtube.com/watch?v=nygn7wB7658

• The magnetic field lines around a wire carrying an

electric current are circular.

Magnetic field lines further apart,
weaker electromagnet

Magnetic field lines are closer,
Stronger electromagnet

• The direction of the magnetic field depends on the
direction of the current flowing in the wire.

• It can be determined by using a simple method called

‘ right – hand grip rule’.

Direction of magnetic field of Electromagnet

(textbook pg161)

compass or Right-hand grip rule.

Direction of magnetic field of Electromagnet

Anti- Clockwise
clockwise
Right-hand grip rule.

Direction of magnetic field of Electromagnet

Clockwise

Anti-clockwise

Right-hand grip rule.

HOW TO DETERMINE THE POLE
(NORTH / SOUTH) OF SOLENOID?

Method 1: Look at the MAGNETIC FIELD LINES

Pointing OUT Pointing IN

It is NORTH pole. It is SOUTH pole.

HOW TO DETERMINE THE POLE
(NORTH / SOUTH) OF SOLENOID?

Method 2:
Look at the direction of current flow of the coil:

IF Clockwise IF Anti-
clockwise
It is SOUTH pole.
It is NORTH pole.

HOW TO DETERMINE THE POLE
(NORTH / SOUTH) OF SOLENOID?

Q: 4 compasses were put around the solenoid.

Please draw the direction of the compass pointer.

sN

HOW TO DETERMINE THE POLE
(NORTH / SOUTH) OF SOLENOID?

Method 2:
Look at the direction of current flow of the coil:

sN

https://www.youtube.com/watch?v=HJRS92i7yfo&list=PLYhvmibZTXNWgTSr5ckyE6N_Kp6
Ywmm_q&index=45

Strength of an
Electromagnet

An electromagnet is stronger

1. if there are more turns in the coil of wire
(solenoid)

Less turns,
weaker electromagnet

more turns,
stronger electromagnet

Strength of an
Electromagnet

An electromagnet is stronger
2. If there is more current flowing through it.

Video: https://www.youtube.com/watch?v=W2nC1zBj4wg

Application of magnets and electromagnets
in daily life

Credit card

Crane

Electric
bell