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A short conductor AB is held parallel to a long thin conductor CD. They carry currents in the same direction. AB is moved (by an external agent) with a constant velocity v, away from CD, in the plane containing AB and CD. AB remains parallel to CD during the motion. How does the power (P) delivered by the external agent depend on time t? (a) P ∝ t. (b) P ∝ 1/t .(c) P ∝ 1/√t.(d) P is independent of t. |
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Answer» Correct Answer is: (b) P ∝ 1/t. The distance between the conductors is x = vt. The magnetic field due to CD on AB is = B = μ0I/4πx. The force on AB is F = Bil. Power, P = Fv = Bilv = (μ0I/4πx) ilv = μ0Iilv/4πvt = μ0Iil/4π . 1/t. ∴ P ∝ 1/t. |
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