A cylindrical conductor of radius carries current only in the -direction

PHYSICS · Single correct · A Level · Physics · Electricity · Electricity

Problem

A cylindrical conductor of radius

R

carries current only in the

x

-direction. In the inner region (

0<r<\tfrac{R}{2}

) the current density has a constant magnitude

J_0

directed

+x

. In the outer region (

\tfrac{R}{2}<r<R

) the current density has constant magnitude

J_1

directed

-x

. If the net current through the conductor’s cross-section must be zero, what must be the value of

J_1

? (a)

J_1 = 3J_0

(b)

J_1 = \dfrac{J_0}{3}

(c)

J_1 = J_0

(d)

J_1 = \dfrac{J_0}{\sqrt{3}}