A straight horizontal rod of mass 50 gm and length 50 cm is placed in uniform horizontal magnetic field of 0.2T perpendicular to X. Calculate the current in X if the force acting on it just balances its weight.(g = 9.8 m/s^2)

Given Information:  

Magnetic field = B = 0.2 T  

Mass of rod = m = 50 g = 0.050 kg  

Length of rod= 50 cm = 0.50 m

Gravitational acceleration = g = 9.8 m/s²

Required Information:  

Current flowing through rod = I = ?

Current flowing through rod = 4.9 A

Explanation:  

The magnetic force produced in a current carrying rod with magnetic field B is given by

F = BILsin(θ)  

This magnetic force is balanced by the weight of the rod which is given by

F = mg

mg = BILsin(θ)

I = mg/BLsin(θ)

Where m is the mass of the rod, L is the length of the rod, B is the magnetic field induced and θ is the angle between magnetic field and current.

I = 0.050*9.8/0.2*0.50*sin(90°)

I = 4.9 A

Therefore, a current of 4.9 A will flow through the rod placed in uniform magnetic field when the force acting on it just balances its weight.

so easy. just google the electromagnetic waves and it’ll pop up.