A coil is placed perpendicular to a magnetic field of 5000 T . When the field is changed to 3000 T in 2 s , an induced emf of 22 V is produced in the coil. If the diameter of the coil is 0 . 02 m , then the number of turns in the coil is:

Step-by-step solution

Average induced EMF is given by, ε = N ∆ ϕ t Also, change in flux ∆ ϕ = ( ∆ B ) A Given: B i = 5000 T , B f = 3000 T d = 0 . 02 m ⇒ r = d 2 = 0 . 01 m Hence, ∆ ϕ = ( ∆ B ) A = 2000 π 0 . 01 2 = 0 . 2 π EMF, ε = N ∆ ϕ t ⇒ 22 = N 0 . 2 π 2 ⇒ N = 70