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Two straight wires A and B of lengths 10...

Two straight wires A and B of lengths 10 m and 12 m carrying currents of 4.0 A and 6.0 A respectively in opposite direction, lie parallel to each other at a distance of 3.0 cm. The force on a 15 cm section of the wire B near its centre is

A

`2.4 xx 10^(-5)N,"attractive"`

B

`2.4 xx 10^(-5)N, "repulsive"`

C

`1.2 xx 10^(-5)N, "attractive"`

D

`1.2 xx 10^(-5)N,"attractive"`

Text Solution

Verified by Experts

The correct Answer is:
B
The lengths of the two wires are quiet large as compared to the separation between them. The two wires many be regarded as infinitely long wires. The force per unit length of wire B due to A,
`f=(mu_(0)I_(1)I_(2))/(2pir)=(4pixx10^(-7)xx4xx6)/(2pixx3xx10^(-2))=1.6xx10^(-4)"N m"^(-1)`
Force on 15 cm or 0.15 cm section of B,
`F=fl=1.6xx10^(-4)xx0.15=2.4xx10^(-5)N` (repulsive).
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