4. Electricity and magnetism
A section of Physics, 5054
Listing 10 of 944 questions
A student makes a 2.0 V battery by connecting two cells of electromotive force (e.m.f.) 2.0 V in parallel. The battery, an ammeter with different ranges and three different resistors are used to set up the circuit shown in . A 2.0 1 2.0 V 2.0 V 3.0 1 X Explain what is meant by electromotive force. State one advantage of using two cells in parallel rather than using a single 2.0 V cell. Resistor X and the 3.0 Ω resistor have a combined resistance that is equal to 2.0 Ω. Calculate the total resistance of the circuit, total resistance = the resistance of X. resistance of X = Determine the reading of the ammeter. reading = Suggest a suitable range for the ammeter. The current in the 2.0 Ω resistor is I2. The current in the 3.0 Ω resistor is I3. The current in X is IX. State the equation that relates I2, I3 and IX. State the potential difference (p.d.) across the 2.0 Ω resistor, p.d. = the 3.0 Ω resistor. p.d. = Question 11 continues on page 18. The student sets up a second circuit using a variable d.c. power supply, an ammeter and a 12 V metal filament lamp. The circuit is shown in Fig. 11. 2. A + d.c. power supply metal filament lamp – The d.c. power supply is set to 12 V and the ammeter reading is 1.5 A. The student changes the e.m.f. of the d.c. power supply to 6.0 V. The lamp dims and the ammeter reading changes. State and explain what happens to the resistance of the metal filament of the lamp. State whether the new ammeter reading is less than, equal to or greater than 0.75 A.
5054_w14_qp_21
THEORY
2014
Paper 2, Variant 1
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An electric circuit contains a 700 Ω resistor and a light-dependent resistor (LDR). is the circuit diagram. oscilloscope LDR S 12 V 700 Ω The electromotive force (e.m.f.) of the battery is 12 V. An oscilloscope is connected across the fixed resistor. shows the oscilloscope, including the settings of the timebase and the Y-gain controls. Line Q shows the position of the trace on the oscilloscope when the switch S is open. timebase Y-gain 50 ms / division 2.0 V / division 1 division P Q The switch S is closed and the trace on the oscilloscope moves to the position shown by line P in . Determine the potential difference (p.d.) across the 700 Ω resistor. p.d. = Determine the resistance of the LDR. resistance = The intensity of the light incident on the LDR gradually increases. State and explain how the trace on the oscilloscope screen moves.
5054_w19_qp_22
THEORY
2019
Paper 2, Variant 2
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shows a wire of length l and cross-sectional area A. l A State how the resistance of the wire in depends on: l A. The cross-sectional area of a piece of metal wire is 7.5 × 10–4 cm2. The resistance of a 1.0 m length of the same wire is 6.4 Ω. The wire is made from metal W. shows a solid cube of side 1.0 cm. It is also made from metal W. 1.0 cm 1.0 cm 1.0 cm A B Calculate the resistance between the two opposite faces A and B of the cube. resistance = The wire in part is taped to a metre rule. shows that a 1.0 m length of the wire (resistance 6.4 Ω) is connected in series with a switch, a cell of electromotive force (e.m.f.) 1.2 V and a resistor of resistance 9.6 Ω. P 0 cm wire 1.2 V 9.6 Ω The switch is closed. Explain what is meant by electromotive force (e.m.f.). Calculate the potential difference (p.d.) across the 1.0 m length of the wire. p.d. = One input terminal of an oscilloscope is connected to the wire at point P, the 0 cm mark of the metre rule. The other terminal of the oscilloscope is connected to a sliding contact. Initially, this contact touches the wire at point P. The Y-gain setting on the oscilloscope is 0.20 V / cm. shows the screen of the oscilloscope with a horizontal trace across the middle of the screen. 1.0 cm 1.0 cm trace The sliding contact is slowly moved along the wire until it reaches the other end of the metre rule. Describe and explain what happens to the trace on the screen. A second, identical 1.2 V cell is connected in parallel with the cell in the circuit in . State one advantage of using two cells in parallel rather than a single cell. State and explain the effect on the trace in of adding the second cell in parallel.
5054_w20_qp_21
THEORY
2020
Paper 2, Variant 1
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The power supply in a circuit is made from several cells, each with the same electromotive force (e.m.f.). The cells are connected in parallel. Explain what is meant by ‘electromotive force’. State one advantage of using several cells in parallel rather than a single cell as the power supply. The power supply is connected in series to a resistor of resistance 4000 Ω and a thermistor. There is a voltmeter in parallel with the resistor. is the circuit diagram. V 4000 Ω power supply thermistor The temperature of the thermistor increases. Explain what happens to the reading on the voltmeter. The e.m.f. of the power supply is 1.5 V. Calculate the reading on the voltmeter when the resistance of the thermistor is 8000 Ω. reading =
5054_w22_qp_22
THEORY
2022
Paper 2, Variant 2
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Questions Discovered
944