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Magnetic Effects of Electric Current
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02/08/2021 12:12 pm
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(a) When does a fuse cut off current? How does it do it?
(b) What is the maximum number of 60 W bulbs that can be run from the mains supply of 220 volts if you do not want to overload a 5 A fuse?
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02/08/2021 12:13 pm
(a) A fuse cuts off current when the current exceeds a safe value (due to short circuiting or overloading). When the current becomes large, it heats the fuse wire too much. Since the melting point of fuse wire is low, it melts and breaks the circuit. Thus, current in the circuit is cut off.
(b) Let the maximum number of bulbs be y.
Power of y bulbs, P = 60y
V = 220V, I = 5A
We know that
P = VI
60y = 220 x 5
60y = 1100
y = 18.33
So, number of bulbs required are 18.