A rectangular loop of sides 20 cm and 10 cm carries a current of 5.0 A. A uniform magnetic field of magnitude 0.20 T exists parallel to the longer side of the loop (a) What is the force acting on the loop? (b) what is the torque acting on the loop?

Explanation

`l = 20 cm = 20 xx 10^(-2) m`,
`w = 10 cm = 10 xx 10 xx^(-2) m`
So, `a = lw = 0.02 m^(2)`,
`I = 5 A`,
`B = 0.2T`
(a) There is no force on the sides ab and cd but the force on the sides ad and be are apposite . So on the loop .
`tau = nia xx B = nia B sin 90^@`
`= 1 xx 5 xx 20 xx 10^(-2) xx 10 xx 10^(-2) xx 0.2`
`= 5 xx 20 xx 10 xx2 xx 10^(-6)`
`= 1000 xx 2 xx 10^(-6)`
`= 2 xx 10^(-2)`
`= 0.02 N m`
Paraller to the shorter side.