46. A copper rod of length ‘I m is rotated about the end perpendicular to a uniform magnetic field of flux density ‘B’ with a constant angular velocity ‘o’. The induced e.m.f. between the two ends is :
(A) 2Blω2
(B) 1/4(Bl2ω)
(C) 1/8(Blω2)
(D) 1/2(Bl2ω)
47. A Universal motor operates at 120 V, 50 Hz. The d.c. voltage to be applied for the same armature current can be :
(A) 240 V
(B) >120 V
(C) 120 V
(D) < 120 V
48. A single-phase 100 V, 50 Hz is applied to a load impedance of 3 12 resistor in series with an inductive reactance of 4 2. The total power supplied is :
(A) 3333 W
(B) 1600 W
(C) 2000 W
(D) 1200 W
49. A cube of a material having a resistivity of p(Ω-m) and area of cross section ‘a’ (m2) has a resistance R(Ω) equal to :
(A) R=ρ/√a
(B) R=ρ√a
(C) R=ρ/a
(D) R=ρa
50. Assume the copper loss equal to iron loss of a transformer at full load.
Calculate the ratio of iron loss to copper loss at half-load,
(A) 4
(B) 0.25
(C) 1
(D) 2.0