A conducting rod of length slides with constant speed on two smooth

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

A conducting rod of length

0.30\,\text{m}

slides with constant speed

2.0\,\text{m\,s}^{-1}

on two smooth, parallel rails that are

0.30\,\text{m}

apart. The rails are connected through a

4\,\Omega

resistor. A uniform magnetic field of

0.60\,\text{T}

is directed perpendicular to the plane of the rails. What magnitude of horizontal force must be applied to the rod to maintain the stated speed? (a)

0.0648\,\text{N}

(b)

0.0016\,\text{N}

(c)

0.016\,\text{N}

(d)

0.162\,\text{N}