Question

Two infinitely long straight wires PQ and RS carrying currents I₁ and I₂ respectively are kept 10 cm apart in vacuum. Calculate magnetic field (B) at the point X shown in Figure 8 below.

Answer 1

Magnetic field at a distance R from current carrying wire is, 

For PQ

B = `mu_0/(2 pi) I/R`

= `(2 xx 10^-7) I/R`    ...`[because mu_0/(2 pi) = (4 pi xx 10^-7)/(2 pi)]`

Given,

I = 4 A

R = 2 × 10⁻²

B₁ = `(2 × 10^(−7))*4/(2 xx 10^-2`

= 4 × 10⁻⁵ T

Similarly (for RS):

B₂ = `(2 xx 10^(-7))*16/(2 xx 10^-2)`

= 4 × 10⁻⁵ T

B₁ and B₂ are equal in magnitude and opposite in direction.

∴ B = B₁ − B₂

= 4 × 10⁻⁵ T − 4 × 10⁻⁵ T

= 0