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Question 1
A student builds a series circuit consisting of a 12 V cell, a 150 Ω lamp, and a 450 Ω resistor. |
a) | Sketch the circuit diagram for the student's circuit. Model answer
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b) | Calculate the total resistance of the lamp and resistor.
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c) | State the equation linking potential difference, current and resistance.
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d) | Calculate the current in the circuit.
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e) | Calculate the potential difference across the lamp.
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f) | Calculate the potential difference across the resistor.
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Question 2
The circuit below is a parallel circuit consisting of two resistors and a cell. |
a) | Draw a voltmeter to measure the potential difference across the 200 Ω resistor.
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b) | State the reading on the voltmeter. 10 V V V
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c) | State the voltage across the 300 Ω resistor. 10 V V V
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d) | Calculate the current through the 200 Ω resistor.
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e) | The 300 Ω resistor has a current of 33.3 mA flowing through it. Calculate the total circuit current.
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Question 3
A student is investigating the current-voltage characteristic of a filament lamp. The student hasn't added an ammeter to measure the circuit current. |
a) | Draw an ammeter on the circuit to measure the current through the lamp.
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b) | Explain why the student uses a variable resistor and not a fixed resistor.
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c) | The student collects the following results. |
c) | The student collects the following results. Model answer Plot the students results.
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d) | The student's results contain an anomalous result. Which result is anomalous?
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e) | Describe what happens to the resistance of the lamp as the voltage is increased from 0 V to 10 V.
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Question 4
A student builds a temperature sensitive circuit with a 12 V cell in series with a lamp and a thermistor. |
a) | At room temperature the thermistor has a resistance of 350 Ω. The potential difference across the lamp is 5 V. Calculate the current flowing through the thermistor.
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b) | The student moves the circuit into a warmer room. Describe what happens to the voltage across the lamp. You may assume the resistance of the lamp stays constant.
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c) | Calculate the power dissipated in the lamp when the voltage across it is 10 V. The resistance of the lamp is 350 Ω. Give your answer to 3 significant figures.
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Question 5
A student is investigating how the resistance of a wire varies with length. |
a) | Add a voltmeter and ammeter to the circuit to measure the potential difference across the wire and the current through the wire.
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b) | The student uses a D.C. power supply. Explain what is meant by a D.C. power supply.
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c) | The student turns off the power supply between readings. Explain why the student must turn the power supply off between readings.
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d) | Describe how the student could use the circuit to identify the relationship between length and resistance.
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e) | The student draws a graph of length against resistance. Draw a line of best fit on the student's graph.
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f) | The student concludes that resistance is directly proportional to the length of the wire. Using data from the graph, show that resistance is directly proportional to length.
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Question 6
A student is investigating the properties of series and parallel circuits. |
When the student closes the switch, the total circuit current is 2.66 A. |
a) | Calculate the current shown on the ammeter.
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b) | The student opens the switch. Describe what happens to the reading on the ammeter and the voltmeter.
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c) | Calculate the reading on the voltmeter.
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d) | The 10 Ω resistor is replaced with a thermistor. The student places the circuit in a cold room. Describe how the voltmeter and ammeter reading will change.
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Question 7
This question is about the relationship between charge, current, and time. |
a) | Define current.
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b) | A filament lamp has a current of 275 mA flowing through it for 2 hours. Calculate the charge that flows through the filament lamp.
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c) | The filament lamp is connected to a 10 V cell. Calculate the energy transferred to the filament lamp in 2 hours.
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Question 8
This question is about electric circuits. |
a) | Calculate the current flowing through S.
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b) | State the potential difference across the resistor R. 10 V V V
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c) | Calculate the potential difference across S.
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d) | Calculate the potential difference across T.
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e) | Calculate the resistance of T at this temperature.
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f) | The student moves the circuit into a warm room. Describe what happens to the potential difference across T.
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Question 9
This question is about LEDs. The student builds a simple circuit consisting of an LED, cell, resistor, voltmeter and ammeter. |
a) | The student has made mistakes setting up the circuit. Redraw the student's circuit to correct the mistakes.
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b) | The current-voltage characteristic for the diode is below. |
Describe the shape of the I-V graph.
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c) | When the voltage across the diode is 1.2 V, the current flowing through it is 17.6 mA. Calculate the resistance of the resistor.
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Question 10
The diagram below shows the wiring for a lighting system in a house. |
a) | State which light bulbs will be turned on with the switches in their current positions. A all turned on B all turned off C 1 and 2 on D 3 and 4 on
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b) | Describe the changes the student would need to make to the switches to turn on bulbs 3 and 4.
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c) | Explain the advantage of using parallel circuits for lighting control.
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d) | The student closes switch A and B. After a short period of time the bulbs stop working. The student suspects that only one of the bulbs has blown. Describe how the student could identify which bulb has blown.
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Question 11
The diagram below shows 4 resistors connected to a 12 V cell of negligible internal resistance. |
a) | Calculate the total resistance of the resistors P, Q, R, and S.
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b) | Calculate the difference between the currents in resistors P and S.
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c) | A voltmeter is connected as shown in the diagram below. Calculate the reading on the voltmeter.
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d) | Describe how the potential difference at X would vary if the cell is replaced with a 10 V cell with internal resistance.
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Question 12
This question is about a temperature sensing circuit. |
a) | The table below shows how the resistance of the thermistor varies with temperature. Model answer Plot a graph of temperature against resistance for the thermistor.
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b) | A heater is added to the circuit so that the heater turns on when the temperature drops below a set value. Draw the location of the heater on the diagram.
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c) | The 1 kΩ heater turns on when the voltage across it is 3 V. Calculate the temperature at which the heater will turn on.
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d) | The 2 kΩ resistor is made of 60 turns of wire that is wound around a non-conducting cylinder of diameter 7.0 mm. The resistivity of the wire is 4.2 x 10-7 Ω m Determine the cross-sectional area of the wire that has been used.
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| 7 | 8 | 9 | 10 | 11 | 12 |