Nuclei — Physics STD 12 Science — Question

Two electric bulbs whose resistances are in the ratio of 1 : 2 are connected in parallel to a constant voltage source. The powers dissipated in them have the ratio

(a) 1 : 2

(b) 1 : 1

(c) 2 : 1

(d) 1 : 4

The slit of a collimator is illuminated by a source as shown in the adjoining figures. The distance between the slit S and the collimating lens L is equal to the focal length of the lens. The correct direction of the emergent beam will be as shown in figure

(a) 1	(b) 3
(c) 2	(d) None of the figures

Antimony and bismuth are usually used in a thermocouple, because

(a) Negative thermal e.m.f. produced	(b) Constant thermal e.m.f. produced
(c) Lower thermal e.m.f. produced	(d) Higher thermal e.m.f. produced

Zener breakdown takes place if

(a) Doped impurity is low	(b) Doped impurity is high
(c) Less impurity in N-part	(d) Less impurity in P-type

The focal length of a concave mirror is 50 cm. Where an object be placed so that its image is two times and inverted

(a) 75 cm

(b) 72 cm

(c) 63 cm

(d) 50 cm

In a crystal, the atoms are located at the position of

(a) Maximum potential energy	(b) Minimum potential energy
(c) Zero potential energy	(d) Infinite potential energy

A condenser of capacity  50μF is charged to 10 volts. Its energy is equal to

(a) 2.5

(b) 2.5

(c) 5

(d) 1.2

A charged particle oscillates about its mean equilibrium position with a frequency of 10⁹Hz. The frequency of electromagnetic waves produced by the oscillator is:

To increase the angular magnification of a simple microscope, one should increase:

1. The focal length of the lens.
2. The power of the lens.
3. The aperture of the lens.
4. The object size.

In a circuit with a coil of resistance 2 ohms, the magnetic flux changes from 2.0 Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is

(a) 5.0 coulomb

(b) 4.0 coulomb

(c) 1.0 coulomb

(d) 0.8 coulomb