4. Electricity and magnetism
A section of Physics, 0625
Listing 10 of 2294 questions
A transformer consists of two coils of insulated wire, wound on a core. State a suitable material from which to make the coils, the core. A lamp has a normal working voltage of 6.0 V. The transformer in is used to enable the 6.0 V lamp to be lit at normal brightness using a 240 V mains supply. 240 V mains 800 turns A B 6.0 V lamp The primary coil has 800 turns. The secondary coil is connected to terminals A and B. Calculate the number of turns in the secondary coil. number of turns = A technician wishes to use the transformer in to light three 6.0 V lamps. What would happen to the lamps if the technician connected them directly across the mains supply? On below, show how the three lamps should be connected to terminals A and B, so that they all light with normal brightness 240 V mains 800 turns A B
0625_s13_qp_22
THEORY
2013
Paper 2, Variant 2
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The transformer in is being used in an attempt to light a lamp using a 120 V a.c. mains supply. The lamp is designed for use in a country where the mains supply is 240 V a.c. 150 turns 300 turns lamp 120 V a.c. 1. Calculate the voltage across the lamp in this arrangement. voltage = V 2. Comment on the brightness of the lamp in this arrangement. The transformer is reversed, so that the 300 turn coil is connected to the 120 V a.c. supply and the 150 turn coil is connected to the lamp. Comment on the brightness of the lamp in this arrangement. Explain your answer. In the National Grid system of electrical energy transmission, a transformer links the power station to the transmission cables, as shown in . power station transformer transmission cables Why is a transformer used here? What has to be done at the other end of the transmission cables, before connection is made to a factory in a town?
0625_s13_qp_23
THEORY
2013
Paper 2, Variant 3
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What is the usual purpose of a transformer? Tick one box. to increase or decrease a.c. to increase or decrease d.c. to turn a.c. into d.c. The transformer in is connected to a 240 V mains supply, and is being used to light a 6.0 V lamp connected between A and B. 240 V mains supply 8000 turns iron 6.0 V lamp A B What name is given to the part of the transformer that is shown on as being made of iron? The primary coil has 8000 turns. 1. State the material from which the coil is usually made. 2. Calculate the number of turns needed on the secondary coil in order to provide 6.0 V between A and B. number of turns = 3. Suggest one difference that is seen in the appearance of the lamp when the mains supply voltage is reduced to 120 V.
0625_s14_qp_23
THEORY
2014
Paper 2, Variant 3
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A battery charger includes a transformer and a rectifier. represents the transformer, consisting of an iron core with two coils P and Q wound on to the core. coil P, 40 000 turns iron core coil Q, 2000 turns P consists of 40 000 turns and Q consists of 2000 turns. When P is connected to a 230 V a.c. supply, there is an e.m.f. across the terminals of Q. Calculate the size of this e.m.f. e.m.f. = Explain how this e.m.f. is generated. The output of Q is connected to the rectifier circuit. State the name of the circuit component that is used in a rectifier circuit to rectify the a.c. (alternating current), the property of this component that is used to rectify the current.
0625_s14_qp_33
THEORY
2014
Paper 3, Variant 3
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