Wave Optics — Physics STD 12 Science — Question

If ‘N’is the number of turns in a coil, the value of self inductance varies as

The temperature coefficient of resistance of a conductor is

(a) Positive always

(b) Negative always

(c) Zero

(d) Infinite

In nuclear fission the percentage of mass converted into energy is about

(a) 10%

(b) 0.01%

(c) 0.1%

(d) 1%

An electron of mass m and charge q is travelling with a speed v along a circular path of radius r at right angles to a uniform of magnetic field B. If speed of the electron is doubled and the magnetic field is halved, then resulting path would have a radius of

(a)

(b)

(c) 2r

(d) 4r

A lens of power +2 diopters is placed in contact with a lens of power – 1 diopter. The combination will behave like

(a) A convergent lens of focal length 50 cm

(b) A divergent lens of focal length 100 cm

(c) A convergent lens of focal length 100 cm

(d) A convergent lens of focal length 200 cm

An air capacitor is connected to a battery. The effect of filling the space between the plates with a dielectric is to increase

(a) The charge and the potential difference	(b) The potential difference and the electric field
(c) The electric field and the capacitance	(d) The charge and the capacitance

A large virtual image of object is formed by :

The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of

(a) 200 V, 50 Hz

(b) 2 V, 50 Hz

(c) 200 V, 500 Hz

(d) 2 V, 5 Hz

If a dielectric substance is introduced between the plates of a charged air-gap capacitor. The energy of the capacitor will

(a) Increase	(b) Decrease
(c) Remain unchanged	(d) First decrease and then increase

The core of a transformer is laminated to reduce energy losses due to

(a) Eddy currents	(b) Hysteresis
(c) Resistance in winding	(d) None of these