Question

A $1\,m$ long wire is lying at right angles to the magnetic field. $A$ force of $1\, kg\, wt$. is acting on it in a magnetic field of $ 0.98\,T $ . The current flowing in it will be

• A. 100 A
• B. 10 A
• C. 1 A
• D. zero

Answer 1

Answer: (B)

Force on a current carrying wire of length $I$, carrying current $I$, kept in a magnetic field $B$ is given by
$F=I 1 \times B=I B l \sin \theta$
where $\theta$ is the angle the wire makes with the magnetic field.
Given, $1=1\, m,\, \theta=90^{\circ}, F =1\, kg - wt =9.8\, N$,
$B=0.98\, T$
$I=\frac{F}{l B}=\frac{9.8}{0.98 \times 1}=10\, A$