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Resistance changes with temperature and lightEdexcel A-Level Physics: Mind map

What this mind map covers

  • The model
  • Metals
  • NTC thermistor
  • LDR
  • Exam tips

Exam questions on Resistance changes with temperature and light

  1. A platinum resistance thermometer uses a coil of platinum wire. The resistance of the coil is 100 Ω at 0 °C and increases steadily as the temperature rises.
    The same p.d. is applied across the coil at a higher temperature. Using I = nqvA, explain what happens to the mean drift velocity of the conduction electrons.2 marks
  2. A light-dependent resistor (LDR) has a resistance of 1.5 kΩ in bright light and 90 kΩ in darkness. It is connected across a 3.0 V cell of negligible internal resistance.
    Explain, in terms of conduction electrons, why the resistance of the LDR is lower in bright light.2 marks
  3. An NTC thermistor has a resistance of 8.0 kΩ at 15 °C and 1.2 kΩ at 60 °C. It is connected across a 5.0 V supply of negligible internal resistance.
    Calculate the power dissipated in the thermistor at 15 °C and at 60 °C.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).