NTA Abhyas JEE Main2020PhysicsMagnetic Effects of CurrentPractice
A wire ab of length l , mass m and resistance R slides on a smooth thick pair of metallic rails joined at the bottom as shown in fig. The plane of the rails makes an angle θ with the horizontal. A vertical magnetic field B exist in the region. If the wire slides on the rails at a constant speed v , then the value of B is -
Options
- Am g R v l 2 cos 2 θ
- Bm g R cos θ v l 2 s i n 2 θ
- Cm g R v 2 l 2 s i n 2 θ
- Dm g R sin θ v l 2 cos 2 θ
Correct answer
D. m g R sin θ v l 2 cos 2 θ
Step-by-step solution
m g sin θ = I l B cos θ = l B cos θ × v B l cos θ R B = m g R s i n θ v l 2 cos 2 θ