Question

A 20 loop coil lies on a table top in a region where the magnetic field is vertically
upward and has a value of 30 Gauss. the field is reduced to zero in 50 sec. If the
radius of each loop is 7.0 cm, what is the average induced emf in the coil (a) while
the field is changing (b) before the field begins to change? (c) As viewed from
above, is the induced e.m.f. in the coil clockwise or anticlockwise? [ 1 Gauss = 1
x 10 – 4
Tesla

Answer 1

$(Eind)_{avg}$ = Δ$\frac{O_{B} }{t}$

⇒  $\frac{O_{i} -O_{f} }{t_{f} -t_{i} }$

⇒ $\frac{20.30.10^{-4}.\pi r^{2}-0 }{50-0}$

⇒ $\frac{6.10^{-2}.3.14.\frac{22}{7}.-7.7.10^{-4} }{50}$

⇒ $184.8.10^{-7}$

⇒ $1.85.10^{-5}V$

Hope it helps:)