Moderate

An electric curren passed through a circuit containing two wires of the same material, connected In parallel. If the lengths and radii of the wires are in the ratio of 4/3 and 2/3, then the ratio of the currents passing through the wire will be

Correct answer: C. 1/3

  • A. 3
  • B. 8/9
  • C. 1/3
  • D. 2

Explanation

To find the ratio of currents in the two wires, we need to use the formula for resistance: R = ρ(L/A), where ρ is resistivity, L is length, and A is the cross-sectional area of the wire. Since the wires are made of the same material, their resistivities are equal.Given that the lengths of the wires are in the ratio 4:3 and their radii in the ratio 2:3, the cross-sectional area A (which is πr²) will be in the ratio (2:3)² = 4:9.Thus, the ratio of resistances R will be (4/3) / (4/9) = 3:1. Since the wires are in parallel, the current is inversely proportional to the resistance. Therefore, the current ratio is 1:3, making option C the correct answer.Option A misapplies the resistance formula, option B miscalculates the impact of the radius, and option D misunderstands the division of current in parallel circuits.

Last updated

About Current Electricity

Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.

Practise Current Electricity

1,052 free Current Electricity MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.

Exams that ask Physics questions like this

Physics is on 13 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.

Related questions