Page 177 - Physics Coursebook 2015 (A level)

Chapter 11: Resistance and resistivity
End-of-chapter questions
1 The graph in Figure 11.12 shows the I –V characteristic of an electrical component. I /A
–6. 6.0 V / V
Figure 11.12 For End-of-chapter Question 1.
a Calculate the resistance of the component when the potential difference across it is:
i 2.0V [2] ii 5.0 V. [1]
b Suggest what the component is. [1]
2 A student connects an NTC thermistor to a battery and an ammeter. He places the thermistor in a beaker of water and gradually heats the water from 10 °C to its boiling point, recording the value of the current as he does so. He then plots a graph of the current in the thermistor against the temperature of the water.
a Sketch the graph you would expect the student to obtain from the experiment. [1]
b Explain how the student could now use the thermistor as a thermometer. [2]
0
–4.0
–2.0
0.40
0.20
–0.20
–0.40
0
2.0
4.0
3 a
b Explain why the resistance of a metallic conductor increases with temperature while that of a
Describe the difference between the conduction processes in copper and in silicon, a semiconductor. [2] semiconductor decreases. [4]
4 A nichrome wire has a length of 1.5 m and a cross-sectional area of 0.080 mm2.The resistivity of nichrome is1.30×10−8Ωm.
a Calculate the resistance of the wire. [2]
b Calculate the length of this wire which would be needed to make an element of an electric heater of
resistance 30 Ω. [2]
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