1) A metal disc of a radius of 100 cm is rotated at a constant angular speed of 60 rad/s in a plane at right angles to an external field of magnetic induction 0.05 Wb/m2. The emf induced between the centre and a point on the rim will be A) 3 V B) 1.5 V C) 6 V D) 9 V Answer: Option BExplanation:Induced emf produced between the centre and a point on the disc is given by e = $\frac{1}{2}\omega BR^{2}$ Putting the values ω = 60 rad/s, $B=0.05 Wb/m^{2}$ and R = 100cm = 1m e = 1/2 × 60 × 0.05 × (1)2 = 1.5 V
