JEE Main202324 Jan 2023Morning ShiftPhysicsMagnetic Effects of CurrentActual
Two long straight wires P and Q carrying equal current 10 A each were kept parallel to each other at 5 cm distance. Magnitude of magnetic force experienced by 10 cm length of wire P is F 1 . If distance between wires is halved and currents on them are doubled, force F 2 on 10 cm length of wire P will be:
Options
- A8 F 1
- B10   F 1
- CF 1 8
- DF 1 10
Correct answer
A. 8 F 1
Step-by-step solution
As we know, force per unit length between two parallel straight wires is given by, F = μ 0 i 1 i 2 2 π d . Therefore, required ratio F 1   F 2 = μ 0 ( 10 ) 2 2 π ( 5 × 10 - 2 ) μ 0 ( 20 ) 2 2 π 5 2 × 10 - 2 = 1 8 ⇒ F 2 = 8 F 1