Electric Current and Ohm's Law Questions and Answers

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Q21
Which law states that current through a conductor is directly proportional to voltage across it?
  • A A) Faraday's Law
  • B B) Lenz's Law
  • C C) Ohm's Law
  • D D) Coulomb's Law
Answer: Option C
Explanation: Ohm's Law states that current through a conductor between two points is directly proportional to the voltage across the two points, at constant temperature.
Q22
Charge is measured in
  • A A) Volt
  • B B) Coulomb
  • C C) Watt
  • D D) Henry
Answer: Option B
Explanation: Electric charge is measured in coulombs (C), where 1 coulomb equals the charge transferred by a current of 1 ampere in 1 second.
Q23
The power dissipated in a resistor of 4 Ω carrying 3 A current is
  • A A) 9 W
  • B B) 12 W
  • C C) 36 W
  • D D) 48 W
Answer: Option C
Explanation: Using the formula P = I²R: P = (3 A)² × 4 Ω = 9 × 4 = 36 W.
Q24
If the voltage is doubled and resistance remains same, current will
  • A A) Halve
  • B B) Double
  • C C) Remain same
  • D D) Be zero
Answer: Option B
Explanation: According to Ohm's Law (I = V/R), current is directly proportional to voltage when resistance is constant.
Q25
The resistance of a wire of length doubled and area halved will be
  • A A) Doubled
  • B B) Quadrupled
  • C C) Halved
  • D D) Unchanged
Answer: Option B
Explanation: Resistance is proportional to length and inversely proportional to area: R ∝ L/A. When L doubles and A halves, R becomes 4 times original.
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