Nuclei — Physics STD 12 Science — Question

A step-up transformer has transformation ratio of 3 : 2. What is the voltage in secondary if voltage in primary is 30 V

(a) 45 V

(b) 15 V

(c) 90 V

(d) 300 V

Referring to the figure below, the effective resistance of the network is

(a) 2 r

(b) 4 r

(c) 10 r

(d) 5r/2

An object is placed 40 cm  from a concave mirror of focal length 20 cm  The image formed is

(a) Real, inverted and same in size	(b) Real, inverted and smaller
(c) Virtual, erect and larger	(d) Virtual, erect and smaller

In charging a battery of motor-car, the following effect of electric current is used

(a) Magnetic

(b) Heating

(c) Chemical

(d) Induction

A square metallic wire loop of side 0.1 m and resistance of 1W is moved with a constant velocity in a magnetic field of 2 wb/m² as shown in figure. The magnetic field is perpendicular to the plane of the loop, loop is connected to a network of resistances. What should be the velocity of loop so as to have a steady current of 1mA in loop

(a) 1 cm/sec

(b) 2 cm/sec

(c) 3 cm/sec

(d) 4 cm/sec

Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to a magnetic field?

1. Electron
2. Proton
3. He⁺
4. Li⁺

A positively charged particle is released from rest in an uniform electric field. The electric potential energy of the charge:

The dimensions of linear charge density is:

A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V.  The potential at the centre of the sphere is

(a) 0 V	(b) 10 V
(c) Same as at point 5 cm away from the surface	(d) Same as at point 25 cm away from the surface

According to the Rutherford’s atomic model, the electrons inside the atom are: