Wave Optics — Physics STD 12 Science — Question

The capacity of a condenser in which a dielectric of dielectric constant 5 has been used, is  C. If the dielectric is replaced by another with dielectric constant 20, the capacity will become

(a)

(b) 4C

(c)

(d) 2C

In Fig. X represents time and Y represent activity of a radioactive sample. Then the activity of sample, varies with time according to the curve

(a) A

(b) B

(c) C

(d) D

Two resistors are connected (a) in series (b) in parallel. The equivalent resistance in the two cases are 9 ohm and 2 ohm respectively. Then the resistances of the component resistors are

(a) 2 ohm and 7 ohm

(b) 3 ohm and 6 ohm

(c) 3 ohm and 9 ohm

(d) 5 ohm and 4 ohm

What is the potential energy of the equal positive point charges of 1μC each held 1 m apart in air

(a) 9

(b) 9

(c) 2 eV/m

(d) Zero

A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An emf is induced in the loop if:

Ratio of magnetic intensities for an axial point and a point on broad side-on position at equal distance d from the centre of magnet will be or The magnetic field at a distance d from a short bar magnet in longitudinal and transverse positions are in the ratio

(a) 1 : 1

(b) 2 : 3

(c) 2 : 1

(d) 3 : 2

If in the circuit shown below, the internal resistance of the battery is 1.5 W and V_P and V_Q are the potentials at P and Q respectively, what is the potential difference between the points P and Q

(a)  Zero

(b) 4 volts (VP > VQ)

(c) 4 volts (VQ > VP)

(d) 2.5 volts (VQ > VP)

One can define ...A... of a place as the vertical plane which passes through the imaginary line joining the magnetic North and the South–poles.

Here, A refers to.

Radio waves and visible light in vacuum have

(a) Same velocity but different wavelength

(b) Continuous emission spectrum

(c) Band absorption spectrum

(d) Line emission spectrum

In a permanent magnet at room temperature.