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An electric current passes through a lon...

An electric current passes through a long straight copper wire. At a distance of 5 cm from the straight wire, the magnetic field is B. What is the magnetic field at a distance of 20 cm from the wire ?

A

`B//6`

B

`B//4`

C

`B//3`

D

`B//2`

Text Solution

Verified by Experts

The correct Answer is:
B
Magnetic field at a distance r from the straight wire.
`B = (mu_(o)i)/(2pi r) " "B prop (1)/(r)`
`(B)/(B.) = (20)/(5) " "B. = (B)/(4)`
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