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A straight wire of length 0.5 metre and carrying a current of 1.2 ampere is placed in a uniform magnetic field of induction 2 tesla. The magnetic field is perpendicular to the length of the wire. The force on the wire is

Asked in CBSE PMT 1992 · Force on a wire in a field

Answer: (2) 1.2 N

Step-by-step solution

Given: L=0.5 m, I=1.2 A, B=2 T, with ⃗B perpendicular to the wire.

Idea: F=BIL sin θ, and a perpendicular field makes sin θ=1.

F=BIL.

F=2×1.2×0.5.

=1.2 N.

The direction is perpendicular to both the wire and the field, given by the left-hand rule for the force on a current.

Why the other options are wrong

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