To measure the temperature coefficient of resistivity α of a semiconductor, an electrical arrangement shown…

To measure the temperature coefficient of resistivity α of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor. The experiment is being conducted at 25°C and resistance of the semiconductor arm is 3 mΩ. Arm BC is cooled at a constant rate of 2 °C s-1. If the galvanometer G shows no deflection after 10 s, then α is:

  1. -2×10-2C-1 ∘
  2. -1.5×10-2C-1 ∘
  3. -1×10-2 C-1∘
  4. -2.5×10-2 C-1∘

Solution

For no deflection(balanced condition) 0.81=R3

⇒R=2.4 mΩ

Temperature fall in 10 s = 20 °C

ΔR=RαΔt

⇒α=ΔRRΔt=2.4-33×20

=-1×10-2 °C-1

Asked in: JEE Main 2024 (01 Feb Shift 2)

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