An electric current passes through a long straight wire. At a distance 5 cm from the wire the magnetic field is `B`. The field at 20 cm from the wire would be
A
B/2
B
B/4
C
B/8
D
B
Text Solution
Verified by Experts
The correct Answer is:
B
`B=(mu_0I)/(2pi a) therefore B prop (1)/(a)` `(B_2)/(B_1)=(a_1)/(a_2) therefore B_2=(B)/(4)`
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