4.2. Electrical quantities
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 319 questions
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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Two lamps, P and Q, are connected to a battery of electromotive force (e.m.f.) 6.0 V and an ammeter, as shown in . A P 6.0 V Q Lamp P has a resistance of 15 Ω. The ammeter reading is 0.65 A. Calculate the current in lamp P. current = Calculate the resistance of lamp Q. resistance = The two lamps are now connected in series to the ammeter and the same battery. In the space below draw the circuit diagram. Explain why the ammeter reading is less than 0.65 A when the lamps are connected in series.
5054_s19_qp_22
THEORY
2019
Paper 2, Variant 2
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A student connects a battery, thermistor X and resistor Y in parallel, as shown in . I E X Y • The electromotive force (e.m.f.) of the battery is E. • The current in X is I. • The resistance of Y is greater than the resistance of X. Tick two boxes, one to show the correct statement about the potential difference across Y and the other to show the correct statement about the current in Y. The potential difference across Y: is less than E is equal to E is greater than E. The current in Y: is less than I is equal to I is greater than I. The student connects thermistor X in series with the resistor Y and a battery of e.m.f. 6.0 V, as shown in . 6.0 V X Y In this circuit, at room temperature, the resistance of thermistor X is 600 Ω and the current in thermistor X is 0.0020 A. Calculate the power produced in the thermistor. power = Calculate the resistance of Y. resistance = The thermistor is cooled. Explain why this causes the potential difference across Y to decrease.
5054_s22_qp_22
THEORY
2022
Paper 2, Variant 2
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Questions Discovered
319