4.4.2. Electrical safety
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 88 questions
shows a 240 V a.c. mains supply connected to a television and two lamps. 40 W 40 W 120 W television neutral live 240 V a.c. supply In normal operation, the power supplied to each lamp is 40 W and the power supplied to the television is 120 W. Calculate, in normal operation, the total power supplied, power = the total number of kilowatt-hours (kW h) of energy supplied to the circuit in 3.0 hours, number of kW h = the current in each lamp. current = Explain why the switches are placed in the live wire and not in the neutral wire.
5054_s17_qp_21
THEORY
2017
Paper 2, Variant 1
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shows a simple relay used to switch a mains electric motor on and off. M springy metal contacts pivot iron armature core coil of wire insulator S mains motor Explain why the motor switches on when switch S is closed. Explain why the core is made of iron rather than steel. A student suggests that the motor can be turned on and off without a relay. He suggests connecting the mains to a simple switch in series with the motor. Suggest one reason why, in some situations, using the relay is better. shows the coil of wire wrapped around a cardboard tube. There is no core. There is an electric current in the wire in the direction shown by the arrows. cardboard tube coil of wire On , draw the pattern of the magnetic field inside and around the coil. Mark the direction of this magnetic field. On , mark the N-pole of the coil. The supply of current to the coil is removed. The ends of the coil are connected to a sensitive ammeter, as shown in . A Describe how a permanent magnet is used to produce a large reading on the ammeter. Explain why a current is produced in .
5054_s20_qp_22
THEORY
2020
Paper 2, Variant 2
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Questions Discovered
88