Question

A horizontal wire $0.1 \,m$ long carries a current of $5 \,A$. The magnitude of the magnetic field which can support the weight of this wire is (assume mass of the wire as $3 \times 10^{-4}\, kg$ )

• A. $0.6 \times 10^{-3} T$
• B. $10 \times 10^{-3} T$
• C. $5.88 \times 10^{-3} T$
• D. $2 \times 10^{-3} T$

Answer 1

Answer: (A)

Force acting on acurrent carrying conductor due to magnetic field $=BIL$
Weight of the wire $=w=m g$
To support $F=W$
BIL$=mg B=m g / I L$
$B=3 \times 10^{-4} \times 9.8 / 5 \times 1$
$B=0.6 \times 10^{-3} T$