6 marksFoundation and HigherRequired practical 156.2.1.3
A student measures the resistance of a length of wire. The diagram shows the correct circuit.
RAV
.1
How is the voltmeter connected to the wire R?
[1 mark]
.2
The voltmeter reads 3.0 V. The ammeter reads 150 mA.
Calculate the resistance of the wire.
[3 marks]
.3
The student switches the circuit off between readings. Suggest why.
[2 marks]
5 marksHigherRequired practical 156.2.1.3
A student measures the resistance of different lengths of the same wire at the same temperature.
Resistance of different lengths of wire: 20 cm, 0.9 ohms; 40 cm, 1.7 ohms; 60 cm, 2.6 ohms; 80 cm, 3.4 ohms; 100 cm, 4.3 ohms.
Length (cm)
Resistance (Ω)
20
0.9
40
1.7
60
2.6
80
3.4
100
4.3
.1
Describe the relationship between the length of the wire and its resistance.
[2 marks]
.2
Use the results to predict the resistance of 150 cm of the same wire.
[2 marks]
.3
Give one variable the student must keep the same.
[1 mark]
6 marksFoundation and HigherRequired practical 166.2.1.4, 6.2.1.3
A student investigates how the current through a component depends on the potential difference across it. They reverse the connections to get the negative values. The graph shows the results.
In the current-potential difference investigation, a student tests a diode, reversing the connections to take readings in both directions. Later, they use a light dependent resistor (LDR) in a circuit.
.1
Describe how the current through a diode depends on the direction of the potential difference.
[2 marks]
.2
In daylight an LDR has a resistance of 400 Ω. The potential difference across it is 6.0 V.
Calculate the current through the LDR in milliamps.
[2 marks]
.3
At night the current through the LDR decreases, even though the potential difference across it stays at 6.0 V.
Explain why.
[2 marks]
6 marksFoundation and HigherRequired practical 156.2.1.3
A student is given a battery, an ammeter, a voltmeter, a metre rule, crocodile clips and a long piece of constantan wire taped to the metre rule.
Plan an investigation into how the length of the wire affects its resistance.
[6 marks]
7 marksFoundation and Higher6.2.1.2, 6.2.1.3
A sensor carries a steady current of 0.040 A for 3.0 minutes. The potential difference across it is 6.0 V.
.1
Calculate the charge passing through the sensor.
[3 marks]
.2
Calculate the resistance of the sensor.
[2 marks]
.3
Explain why the current entering and leaving the sensor is the same.
[2 marks]
6 marksFoundation and HigherRequired practical 166.2.1.4, 6.2.1.3
During an I-V investigation a filament lamp takes 0.20 A at 1.0 V and 0.50 A at 6.0 V.
.1
Calculate the resistance at 1.0 V.
[2 marks]
.2
Calculate the resistance at 6.0 V.
[2 marks]
.3
Explain the change in resistance as the potential difference increases.
[2 marks]
6 marksHigher6.2.1.4
At fixed potential difference 3.0 V, a thermistor carries 0.0020 A in cool water and 0.0060 A in warm water. It is the type whose resistance falls as temperature rises.
.1
Calculate the resistance in cool water.
[2 marks]
.2
Calculate the resistance in warm water.
[2 marks]
.3
A pupil says the current tripled because the supply voltage tripled. Evaluate the statement using the data.
[2 marks]
5 marksFoundation and HigherRequired practical 156.2.1.3
A student measures the resistance of 0.20 m, 0.40 m and 0.60 m of one uniform wire. Values are 1.6 Ω, 3.2 Ω and 5.6 Ω. The 0.60 m measurement is made after current has flowed for several minutes.
.1
Use the first two results to calculate the expected resistance of 0.60 m of wire at the original temperature.
[2 marks]
.2
Evaluate the final result and suggest how to improve the investigation.