4. Electricity and magnetism
A section of Physics, 5054
Listing 10 of 944 questions
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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Use EITHER The Y-plates of a cathode-ray oscilloscope (CRO) are connected to an alternating voltage of amplitude 4.0 V and frequency 25 Hz. The Y-gain of the CRO is set at 2.0 V / division and the time-base is set at 0.01 s / division. On the grid below, draw the trace on the screen of the CRO. Show your calculations beside the grid. one division OR shows a transistor used in the circuit of a simple moisture detector. metal contacts water lamp transistor Describe what happens when the water level in the beaker reaches the metal contacts. State one use for this simple moisture detector.
5054_w07_qp_2
THEORY
2007
Paper 2, Variant 0
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shows a 9.0 V battery connected in series with a 16.0 Ω resistor and a small metal conductor X at room temperature. V 16.0 Ω X 9.0 V A voltmeter measures the potential difference (p.d.) across the 16.0 Ω resistor. At room temperature the resistance of X is 4.0 Ω. Calculate the current supplied by the battery. Calculate the p.d. across the 16.0 Ω resistor. X is heated slowly to a very high temperature. Sketch a graph to show how the resistance of a metal conductor depends on its temperature. State and explain how the voltmeter reading changes as the temperature of X rises. Suggest a suitable range for the voltmeter. There is a choice of part on the following page. EITHER Describe in outline how the circuit in can be used as a thermometer. State two advantages of a thermometer such as this over a liquid-in-glass thermometer. The change in voltmeter reading with temperature is non-linear. Explain what is meant by non-linear. OR The voltmeter is removed from the circuit in and the negative terminal of the battery is earthed. A connection is made from the circuit to the inputs A and B of a NAND gate. The output of the NAND gate is connected to an LED (light-emitting diode) and a resistor. This is shown in . 16.0 Ω X 9.0 V LED A B Draw the truth table for a NAND gate. The LED is lit. State the inputs at A and B and explain why these inputs cause the LED to light. X is slowly heated to a very high temperature. At a certain temperature, the LED switches off. Explain why this happens.
5054_w09_qp_2
THEORY
2009
Paper 2, Variant 0
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11 An ammeter, a variable resistor and a 4.0 Ω resistor are connected in series with a 6.0 V battery. A cathode-ray oscilloscope (c.r.o.) is connected in parallel with the 4.0 Ω resistor through a switch. is the circuit diagram. A 6.0 V switch c.r.o. 4.0 Ÿ The switch is open. The variable resistor is adjusted so that it has a resistance of 8.0 Ω. Calculate the current measured by the ammeter, current = the potential difference (p.d.) across the 4.0 Ω resistor. p.d. = The resistance of the variable resistor is adjusted until the p.d. across the 4.0 Ω resistor is 5.0 V. State the effect that this adjustment has on the current measured by the ammeter, the resistance of the variable resistor. The trace on the c.r.o. is a horizontal line across the middle of the screen and the p.d. across the 4.0 Ω resistor is still 5.0 V. The Y-gain control is set at 2.0 V / cm and the switch is closed. State the effect on the trace of closing the switch. shows, in outline, the basic structure of a c.r.o. viewed from the side. ILODPHQW HOHFWURQEHDP On write, in the five empty boxes, the names of the parts of the c.r.o. indicated. Explain how the electron beam is produced. Explain why the tube of the c.r.o. must be evacuated. Question 11 continues on page 16. In the c.r.o. shown in , the electrons travel from left to right. 1. Explain why the flow of electrons is an electric current. 2. State the direction of the conventional current due to the electrons.
5054_w13_qp_21
THEORY
2013
Paper 2, Variant 1
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944