Lesson eLearning

Which of the following statements correctly explains why the resistance of a metal conductor increases when it is heated?

medium MCQ 1 mark Class 7 · Science · Electric Current and its Effects
  1. The number of free electrons increases.
  2. The lattice vibrations increase, causing more collisions.
  3. The length of the conductor decreases.
  4. The temperature reduces resistivity.
Answer
The lattice vibrations increase, causing more collisions.

The correct answer is The lattice vibrations increase, causing more collisions. — Select option B as the correct explanation.

Step-by-step solution

  1. Identify that resistance of metals depends on electron–lattice interactions.
  2. Recognise that heating increases lattice vibrations, leading to more electron collisions and higher resistance.
  3. Reject options: free electrons do not increase, length does not decrease, temperature does not reduce resistivity in metals.
  4. Select option B as the correct explanation.
Common mistake: Choosing that free electron count increases resistance.

Concept tested: Temperature effect on metal conductors

Published · How this solution was prepared and checked

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