Question

A straight wire having mass of 1.2 kg and length of 1 m carries a current of 5 A. If the wire is suspended in mid-air by a uniform horizontal magnetic field, then the magnitude of field is

• A. 0.65 T
• B. 1.53 T
• C. 2.4 T
• D. 3.2 T

Answer 1

Answer: (C)

2.4 T

Answer 2

For mid-air suspension the upward force F on wire due to magnetic field B must be balanced by the force due to gravity then

Here, $\mathrm { m } = 1.2 \mathrm {~kg} , \mathrm {~g} = 10 \mathrm {~ms} ^ { - 2 } , \mathrm { I } = 5 \mathrm {~A} , \mathrm { l } = 1 \mathrm {~m}$