4.2.4. Resistance
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 149 questions
A student connects a thermistor in series with a battery and an ammeter. He uses the resistance of the thermistor to determine temperature. In the space below, draw a circuit diagram showing the thermistor, the battery and the ammeter. The student places the thermistor in a water bath at various temperatures and records the reading on the ammeter. shows how the current varies with temperature. 0.10 0.20 current / A 0.30 0.40 temperature / °C The potential difference (p.d.) across the thermistor remains constant. The resistance of the thermistor is 240 Ω at a temperature of 20 °C. Using , calculate 1. the potential difference (p.d.) across the thermistor, p.d. = 2. the resistance of the thermistor at a temperature of 40 °C. resistance = The resistance of the thermistor is 240 Ω at a temperature of 20 °C and 48 Ω at a temperature of 60 °C. The resistance of the thermistor does not change linearly with temperature. Describe how the resistances at 20 °C, 40 °C and 60 °C show this is true. A thermocouple thermometer is another type of thermometer. Describe the structure of a thermocouple thermometer. You may draw a diagram if you wish. State two advantages of a thermocouple thermometer over a liquid-in-glass thermometer. 1. 2.
5054_s17_qp_21
THEORY
2017
Paper 2, Variant 1
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A student uses the circuit shown in to investigate a resistor R. A V R Describe how the student uses the apparatus in to obtain a range of ammeter and voltmeter readings. The readings obtained are shown in Table 5.1. Table 5.1 voltmeter reading / V ammeter reading / mA 7.6 5.2 2.4 State Ohm’s law. Using the results in Table 5.1, show that the resistor obeys Ohm’s law. The student has available an ammeter with five ranges marked: • 0 − 10 A • 0 − 200 mA • 0 − 20 mA • 0 − 2 mA • 0 − 0.2 mA Suggest how the student makes best use of the different ranges during the investigation.
5054_s19_qp_21
THEORY
2019
Paper 2, Variant 1
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shows the circuit diagram of a temperature gauge. It contains an ammeter, a thermistor, a fixed resistor R and a battery. A thermistor R The current is measured at different temperatures and a graph of the results is shown in . 0.005 0.010 0.015 0.020 0.025 temperature / °C current / A State how the resistance of the thermistor changes with temperature and explain how shows this change. Resistance and current are used for the measurement of temperature. State one other physical property that is used for the measurement of temperature. A temperature scale involves the use of fixed points. State what is meant by: the ice point the steam point. At 80 °C, the potential difference (p.d.) across the thermistor is 3.6 V. State what is meant by potential difference. Calculate the resistance of the thermistor when the temperature is 80 °C. resistance = The electromotive force (e.m.f.) of the battery is 25 V. Calculate the resistance of the resistor R. resistance = The current scale on the ammeter is linear. Using values from , a student marks the scale on the ammeter with temperature values that correspond to the values of the current. The temperature is then read directly from the temperature scale on the ammeter. State what is meant by a sensitive thermometer. State and explain at which temperatures this thermometer is most sensitive. The temperature gauge is used to measure the temperature of a room. Suggest why the temperature obtained using the gauge is slightly higher than the actual temperature of the room.
5054_s20_qp_22
THEORY
2020
Paper 2, Variant 2
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Questions Discovered
149