NTA Abhyas JEE Main2020PhysicsElectromagnetic InductionPractice
A conducting rod of resistance r moves uniformly with a constant speed v in a uniform magnetic field. If the rod keeps moving uniformly, then the amount of force required is
Options
- Av B 2 l 2 R
- B2 v B 2 l 2 R + r
- Cv B 2 l 2 R + r
- Dzero
Correct answer
C. v B 2 l 2 R + r
Step-by-step solution
F → = i ∫ d l → × B → ⇒ F = i l B i = e i n ( R + r ) When conducting rod moves in crossed magnetic field constant velocity v , emf is induced = B v l ⇒   i = B v l R + r ∴   F = v B l R + r l B = v B 2 l 2 R + r