Page 169 - Physics Form 5 KSSM_Neat

Discussion: CHAPTER 4
1. What is the effect of the motion of the bar magnet on Note
the polarity of the magnet at end A of the solenoid?
Induced current is produced Electromagnetism
2. Predict the polarity of the magnet produced at end A: in the solenoid by the relative
(a) when the south pole of the bar magnet is pushed towards it motion between the bar magnet
(b) when the south pole of the bar magnet is pulled away from it and the solenoid.
KEMENTERIAN PENDIDIKAN MALAYSIA

For a solenoid, Lenz's law is used to determine the magnetic polarity at the end of the
solenoid when current is induced. Lenz's law states that the induced current always flows in a
direction that opposes the change of magnetic flux that causes it. Figure 4.28 shows that Lenz’s
law is used to determine the direction of induced current in a solenoid.
a 1 Magnet pushed b 1 Magnet pushed

towards solenoid towards solenoid
S N N S
N S S N
2 Induced current 2 Induced current
S
produces a north produces a south
pole at the end of pole at the end of
the solenoid to repel the solenoid to repel
0 0
the magnet moving the magnet moving
towards the solenoid towards the solenoid
c 1 Magnet pulled d 1 Magnet pulled

away from solenoid away from solenoid

N S S N
N S S N
2 Induced current 2 Induced current
produces a south produces a north
pole at the end of the pole at the end of the
solenoid to attract the solenoid to attract the
0 0
magnet moving away magnet moving away
from the solenoid from the solenoid

Figure 4.28 Lenz's law used to determine the direction of induced current in a solenoid
Direct Current Generator and Alternating
Current Generator

Photograph 4.5 shows wind turbines electric
generators that apply electromagnetic induction
to produce induced e.m.f. There are two types
of generators – the direct current generator and
alternating current generator. What is the working
principle of these current generators?

Photograph 4.5 Wind turbines at Kuala Perlis

LS 4.2.3 4.2.4 159