KCET 2015 Physics Solved Paper

Consider the two parallel wires as shown in the following figure.Now, force experienced by the two wires is
F=‌

µ0

4π

‌

2I1I2

d

We know I1=1A;I2=3A;d=1m and ‌

µ0

4π

=10−7
Therefore, F=‌

10−7×2×1×3

1

=6×10−7
and since the currents are in opposite directions, therefore, force experienced will be repulsive
So, the force per unit length acting between two wires is 6×10−7Nm−1 and it is repulsive.