(i) Midway between R and S
Field due to R, BR=μ0I2πr
Field due to S, BS=μ0I2πr
=4π×10−7×302π×0.05=12×10−5T
∵ Direction of B due to two wires are opposite,
B=BR+BS=0
Hence, total flux density is zero.
(ii) If P is 0.05 m from R and 0.15 m from S
BR=μ0I2πr=4×10−72π×0.05
=4×10−5T
BS=μ0I2πr=4π×10−7×302π×0.15
∵BR and BS are in the same direction
∴ Resultant field =BS+BR=2×10−7(100.05+300.15)=8×10−4T
Hence, total flux density is 8×10−4Weber