4.3. Electric circuits
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 85 questions
shows two pieces of soft iron in the magnetic field of a strong permanent magnet. N pole of magnet S pole of magnet soft iron The pieces of soft iron become magnetised. On , mark the magnetic poles produced at each end of both pieces of soft iron. shows a reed switch. soft iron glass The reed switch is placed between the poles of the strong permanent magnet. State and explain what happens. shows two separate electrical circuits. warning lamp coil thermistor One circuit consists of a reed switch, a cell and a warning lamp. The other circuit consists of a thermistor, another cell, and a coil wound round the reed switch. The thermistor is at the same temperature as the air around it. State what happens to the thermistor when the temperature of the air rises. Explain why the warning lamp lights up when the air temperature rises.
5054_s09_qp_2
THEORY
2009
Paper 2, Variant 0
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shows a variable potential divider connected to a 6.0 V battery. A movable contact output voltage B 6.0 V The movable contact can slide between A and B. As it moves, the output voltage changes. Complete the table below to show the output voltage when the contact is at A and at B. position of movable contact A B output voltage shows a thermistor in a potential divider circuit that is used to monitor temperature. The fixed resistor has a resistance of 2000 Ω. A thermistor 2000 1 6.0 V Explain why the voltage across the thermistor decreases as its temperature rises. At one temperature, the thermistor has a resistance of 1000 Ω. Calculate the current in the thermistor. current =
5054_s14_qp_21
THEORY
2014
Paper 2, Variant 1
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A thermocouple thermometer is made from two different metals and a voltmeter. One junction of the thermocouple thermometer is placed in a beaker containing a mixture of water and ice. The other junction is placed inside a high-temperature furnace, as shown in . metal 1 metal 2 water and ice high- temperature furnace V The thermocouple thermometer has a linear output over the operating temperature range of the furnace. State what, for a thermocouple thermometer, is meant by a linear output. The junction inside the furnace is at temperature T. shows the reading V of the voltmeter at two values of T that are within the operating temperature range of the furnace. T / °C V / mV 6.20 7.70 When the furnace is operating at a high temperature, the furnace door is opened and the reading of the voltmeter falls to 6.80 mV. Calculate the temperature of the junction inside the furnace. temperature = State why a liquid-in-glass thermometer is not used to measure the temperature inside the furnace.
5054_w12_qp_21
THEORY
2012
Paper 2, Variant 1
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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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Questions Discovered
85