Atoms — Physics STD 12 Science — Question

The negative Zn pole of a Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is

(a) 0.242 g

(b) 0.190 g

(c) 0.141 g

(d) 0.126 g

Due to the earth's magnetic field, charged cosmic ray particles

(a) Require greater kinetic energy to reach the equator than the poles

(b) Require less kinetic energy to reach the equator than the poles

(c) Can never reach the equator

(d) Can never reach the poles

A small square loop of wire of side l is placed inside a large square loop of wire of side L (L > l). The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to

(a) l / L

(b)

(c) L/l

(d)

The negative of the work done by the conservative internal forces on a system equals the change in:

1. T​​​​​otal energy.
2. Kinetic energy.
3. Potential energy.
4. None of these.

Two conducting spheres of radii 5 cm and 10 cm are given a charge of 15 μC  each. After the two spheres are joined by a conducting wire, the charge on the smaller sphere is

(a) 5 μC

(b) 10 μC

(c) 15 μC

(d) 20 μC

The continuous x-ray spectrum obtained from a Coolidge tube is of the form

(a)

(b)

(b)

(d)

Diffraction effects are easier to notice in the case of sound waves than in the case of light waves because

(a) Sound waves are longitudinal	(b) Sound is perceived by the ear
(c) Sound waves are mechanical waves	(d) Sound waves are of longer wavelength

The radius of curvature of a concave mirror is 0.80 cm, its focal length in meters will be :

Carbon resistors are of two types: