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NEETPhysicsCurrent Electricity

An electric bulb is rated 100 W, 200 V. When it is connected across a fluctuating supply line, the power dissipated by the bulb is found to be 64 W. Assuming the resistance of the bulb remains constant, what is the actual line voltage applied to the bulb?

Options

  1. A128 V
  2. B160 V
  3. C250 V
  4. D64 V

Correct answer

B. 160 V

Step-by-step solution

The resistance of the bulb is constant and is related to its rated values by R = V_ rated ^2 P_ rated . The actual power consumed when connected to the line is P_ actual = V_ actual ^2 R . Dividing the two equations, we get: P_ actual P_ rated = ( V_ actual V_ rated )^2 Substituting the given values: 64 100 = ( V_ actual 200 )^2 Taking the square root on both sides: 8 10 = V_ actual 200 V_ actual = 200 0.8 = 160 V. Answer: 160 V

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