section 16.3 electromagnet
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Section 16.3Section 16.3
ElectromagnetElectromagnet
Section 16.3Section 16.3
ElectromagnetElectromagnet
Factors affecting the strength ofFactors affecting the strength of
electromagnetelectromagnet
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it works as magnetwhen there is a flow of
I
16.3 Electromagnet (SB p. 117)
Electromagnet
electromagnet
Go to
Discussion 3Discussion 3
can change fieldstrength
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16.3 Electromagnet (SB p. 118)
Electromagnet
soft iron
cores
low voltage d.c.power supply
strongly magnetized
demagnetized
switch off
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Expt. 16C
Electromagnet d.c.power supply
soft-iron rod
paper clips
solenoid
16.3 Electromagnet (SB p. 118)
Electromagnet
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electromagnet attractspaper clips
16.3 Electromagnet (SB p. 119)
Electromagnet
use compass to finddirection of field
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S N
direction of current reversed
16.3 Electromagnet (SB p. 119)
Electromagnet
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Factors affecting the strength of
electromagnet
Thinking 5Thinking 5
16.3 Electromagnet (SB p. 119)
Strength of electromagnet
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Discussion 4Discussion 4
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To section 16.4
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Discussion 3:Discussion 3:
1. How can you produce a magnetic field otherthan using a permanent magnet?
2. Compare the magnetic field produced in step 1
with that produced from a permanentmagnet. Which one is more practical? Why?
Discuss with your classmates.Ans
wer1. Pass a current through a conducting wire.
16.3 Electromagnet (SB p. 117)
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2. The method we suggested is more practical because
we can change the polarity and strength of the
electromagnet easily.
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Thinking 5Thinking 5
Which of the following can increase the strengthof the electromagnet in the figure?
(a) Replace the steel rod with a soft iron rod.
(b) Replace the resistor with the one of lowerresistance.
(c) Decrease the number of turns in the solenoid.
Answer
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(a) and (b). In (b), the current
increases if the resistance of
the resistor decreases.
16.3 Electromagnet (SB p. 119)
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Discussion 4:Discussion 4:
Fig. (a) shows the structure of a typical electric
bell. How does it work? Explain briefly.
Ans
wer
16.3 Electromagnet (SB p. 120)
Fig. (a) Fig. (b)
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Discussion 4: (Cont)Discussion 4: (Cont)
When the push button is pressed, a current
flows through the circuit and the electromagnet
magnetizes the soft-iron armature which forms a part
of the handle of the hammer. The hammer is then
attracted by the electromagnet and hits the gong toproduce a sound. At the same time, the contact breaks
the circuit at A. Then the spring pulls the hammer
back to its original position and the circuit is closed
again. The whole process repeats itself as long as the
button is pressed. It allows the bell to ring
continuously.
16.3 Electromagnet (SB p. 120)
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