Question

A straight wire of diameter 0.5 mm carrying a current of 1 A is replaced by another wire of 1 mm diameter carrying the same current. The strength of magnetic field far away is

• A. Twice the earlier value
• B. Half of the earlier value
• C. Quarter of its earlier value
• D. Unchanged

Answer 1

Answer: (D)

Unchanged

Answer 2

The magnetic field is given by $B = \frac { \mu _ { 0 } } { 4 \pi } \frac { 2 i } { r }$ .

It is independent of the radius of the wire.