4.5.2. The a.c. generator
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 30 questions
An a.c. generator produces alternating current. Draw a labelled diagram of a simple a.c. generator. Explain how the current is generated. The output of the generator is connected to the terminals of a cathode-ray oscilloscope. shows the trace produced on the screen of the oscilloscope. trace 1 division Each vertical division on the scale in represents 2 volts. Describe how you would check that one vertical division represents 2 volts. The trace in is too small and is at the bottom of the screen. Adjustments are made to the oscilloscope controls to produce the trace in . State and explain the adjustments made to the oscilloscope controls. Explain how the beam of electrons is produced inside the cathode-ray oscilloscope.
5054_s09_qp_2
THEORY
2009
Paper 2, Variant 0
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EITHER shows a simple a.c. generator. The coil is turning and an e.m.f. is induced in the coil. D[LV FRLO VOLSULQJ RXWSXW The generator contains a permanent magnet. State the name of a metal used in a permanent magnet. At the instant shown in , the induced e.m.f. is a maximum. Explain why the induced e.m.f. is a maximum. State the position of the coil where there is no induced e.m.f. OR shows an astable circuit (pulse generator) that contains two capacitors C1 and C2, two resistors R1 and R2, and two components labelled Y. 0 V output Q output P Y Y C2 C1 R2 R1 State the name of component Y. Complete to show the truth table for component Y. A high voltage is shown as 1 and a low voltage as 0. input output The astable circuit produces a series of pulses at output Q. At one instant, capacitor C1 is uncharged, output P is 1 and output Q is 0. Describe how the voltage across resistor R1 changes until Q becomes 1. Describe one change to the circuit that increases the frequency of the astable circuit.
5054_s13_qp_22
THEORY
2013
Paper 2, Variant 2
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shows a simple a.c. generator. coil rotation of coil output voltage S N The coil rotates and an alternating electromotive force (e.m.f.) is induced in the coil. shows how the alternating e.m.f. varies with time as the coil rotates. + e.m.f. time – Explain why an e.m.f. is induced, why the e.m.f. is sometimes positive and sometimes negative. Changes are made to the a.c. generator, one at a time: • stronger magnets are used • more turns are wound on the coil • the coil is turned faster. Complete the table in to show what happens to the maximum value of the e.m.f. and to the frequency of the alternating e.m.f. changes made what happens to the maximum value of the e.m.f. what happens to the frequency of the e.m.f. stronger magnets more turns on the coil the coil is turned faster
5054_s15_qp_22
THEORY
2015
Paper 2, Variant 2
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shows a simple a.c. generator. N S coil slip rings voltage output coil A B brush Explain why there is a voltage induced in the coil when the coil is turned. In the coil is horizontal, with side AB on the left. The output voltage is +6.0 V. On draw a line from each of the shaded boxes to one of the circled voltages to show the voltage output when the coil is in different positions. One line has been drawn for you. coil horizontal with AB on the left coil horizontal with AB on the right coil vertical with AB on the top coil vertical with AB on the bottom +6.0 V 0 V –6.0 V Both an a.c. generator and a d.c. motor contain a coil and brushes. shows how the brushes are connected to the coil in an a.c. generator. Draw a diagram to show how the brushes are connected to the coil in a d.c. motor. State why there are forces on the sides of the coil in a d.c. motor.
5054_s23_qp_21
THEORY
2023
Paper 2, Variant 1
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Questions Discovered
30