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Current Electricity — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsCurrent Electricity1 Mark
Question
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion: Heater wire must have high resistance and high melting point.
Reason: If resistance is high, the electric conductivity will be less.
✓

Answer

  1. Both A and R are true, but R is not the correct explanation of A.
Explanation:
Heater wire must have high resistance and high melting point, because in series current remains same, therefore according to Joule's law $\text{H} = \frac{\text{i}^2\text{Rt}}{4.2}$ heat produced is high if R is high. Melting point must be high, so that wire may not melt with increase in temperature.

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