Electrostatics — Physics STD 12 Science — Question

The core of a transformer is laminated so that(a) Ratio of voltage in the primary and secondary may be increased(b) Rusting of the core may be stopped(c) Energy losses due to eddy currents may be reduced(d) Change in flux is increased

What name is given to a cylindrical coil of diameter less than its length?

Match the List I with the List II from the combination shown. In the left side (List I) there are four different conditions and in the right side (List II), there are ratios of heat produced  in each resistance for each condition :

List I		List II
(I)	Two wires of same resistance are connected in series and same current is passed through them	(A)	1 : 2
(II)	Two wires of resistance R and 2R ohm are connected in series and same P.D. is applied across them	(B)	4 : 1
(III)	Two wires of same resistance are connected in parallel and same  current is flowing through them	(C)	1 : 1
(IV)	Two wires of resistances in the ratio 1 : 2 are connected in parallel and same P.D. is applied across them	(D)	2 : 1

(a) I – B; II – A; III – C; IV - D(b) I – C; II – D; III – C; IV - D(c) I – B; II – D; III – A; IV - C(d) I – A; II – B; III – D; IV - C

When ultraviolet rays fall on the surface of metal, photoelectric effect does not occur but the following will casue :

When a capillary tube is dipped into a liquid, the liquid neither rises nor falls in the capillary.

Television signals broadcast from the moon can be received on the earth while the TV broadcast from Delhi cannot be received at places about 100 km distant from Delhi. This is because(a) There is no atmosphere around the moon(b) Of strong gravity effect on TV signals(c) TV signals travel straight and cannot follow the curvature of the earth(d) There is atmosphere around the earth

An electric motor operates on a 50 volt supply and a current of 12A. If the efficiency of the motor is 30%, what is the resistance of the winding of the motor(a) 6 Ω(b) 4 Ω(c) 2.9 Ω(d) 3.1 Ω