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A heating element has a resistance of 100 Ω at room temperature. When it is connected to a supply of 220 V , a steady current of 2 A passes in it and temperature is 500 o C more than the room temperature. The temperature coefficient of resistance of the heating element is

Options

  1. A5   × 10 - 4     o C - 1
  2. B2   × 10 - 4     o C - 1
  3. C1   × 10 - 4     o C - 1
  4. D0.5   × 10 - 4     o C - 1

Correct answer

B. 2   × 10 - 4     o C - 1

Step-by-step solution

Resistance of heating element after temperature increases by 500   o C = 220 2 = 110   Ω (from Ohm's law). The new resistance is related to the temperature coefficient of the heating element as 110 = 100   ( 1 + α 500 ) α = 10 100   × 500 ⇒ α = 2   × 10 - 4   ° C - 1

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