A wheel with 8 metallic spokes each 50cm long is rotated with a speed of 120rev /min The - Physics - Magnetism And Matter

Question

A wheel with 8 metallic spokes each 50cm long is rotated with a
speed of 120rev /min The earth's magnetic field at the place is 0
4G and the angle of dip is 60 Calculate the emf induced between the
axle and the rim of the wheel How will the value of emf be affected
if the number of spokes were increased ?

Neha Gupta · Accepted Answer

Vertical component of earth magnetic field is given by:Bv= BsinδB = 0
4 Gδ = 60Bv = Bsin60Bv = 0
4×32Bv= 0 692 G = 0
692 ×10-4 teslalength of the stroke will act as the diameter
radius r = 502r = 25cm = 0
25 mArea a = πr2a = 3 14×0
25×0 25a = 0 19 m2
ω = 2πνν = 120 revolution per min = 2 rev per secondω = 2×3
14×2 ω= 12
56 rad per secondinduced emf is one stoke e = Bvaωcosωte = 0
692×10-4×0 19×12
56 cosωte = 0
1×10-3 volt  = 0
1 milli voltfor the 8 stokese = 8×0
1 milli volte = 0
8 milli voltas no of stokes increases
induced emg increases