# A magnet has coercivity of 3×103 Am−1. It is kept in a 10cm long solenoid with a total of 50 turns. How much current has to be passed through the solenoid to demagnetize it?

#### μ∘H=μ∘nIGiven:

where H=3×10−3Am−1=coercivity

n=number of turns per unit length =500.1=500m−1

To find: I= current

Now

H=nI

I=6×10−6A=6μA