JUNE 2024 — Physics STD 12 Science — Question

Shown in the figure here is a convergent lens placed inside a cell filled with a liquid. The lens has focal length + 20 cm when in air and its material has refractive index 1.50. If the liquid has refractive index 1.60, the focal length of the system is

(a) + 80 cm

(b) – 80 cm

(c) – 24 cm

(d) –100 cm

A man of length h requires a mirror, to see his own complete image of length at least equal to

(a)

(b)

(c)

(d) h

100 cells each of e.m.f. 5 V and internal resistance 1 ohm are to be arranged so as to produce maximum current in a 25 ohms resistance. Each row is to contain equal number of cells. The number of rows should be

(a) 2

(b) 4

(c) 5

(d) 10

A spherical condenser has inner and outer spheres of radii a and b respectively. The space between the two is filled with air. The difference between the capacities of two condensers formed when outer sphere is earthed and when inner sphere is earthed will be

(a) Zero

(b) 4π

(c)  4π

(d) 4 π

An e.m.f. of 12 volt is produced in a coil when the current in it changes at the rate of 45 amp/minute. The inductance of the coil is

(a) 0.25 henry

(b) 1.5 henry

(c) 9.6 henry

(d) 16.0 henry

A circular loop of radius 0.0157m carries a current of 2.0 amp. The magnetic field at the centre of the loop is (

(a) 1.57	(b) 8.0
(c) 2.5	(d)  3.14

When a resistance of 2 ohm is connected across the terminals of a cell, the current is 0.5 A. When the resistance is increased to 5 ohm, the current is 0.25 A. The e.m.f. of the cell is

(a) 1.0 V

(b) 1.5 V

(c) 2.0 V

(d) 2.5 V

Electric conduction in a semiconductor takes place due to:

The idea of parmanu was given by: