Electric Charges and Fields — Physics STD 12 Science — Question

A ray of light is incident at the glass–water interface at an angle i, it emerges finally parallel to the surface of water, then the value of  would be

(a) (4/3) sin i

(b) 1/sin i

(c) 4/3

(d) 1

A cell of internal resistance 3 ohm and emf 10 volt is connected to a uniform wire of length 500 cm and resistance 3 ohm.  The potential gradient in the wire is

(a) 30 mV/cm

(b) 10 mV/cm

(c) 20 mV/cm

(d) 4 mV/cm

If a copper rod carries a direct current, the magnetic field associated with the current will be:

In a Young’s double slit experiment, the source illuminating the slits is changed from blue to violet. The width of the fringes

(a) Increases

(b) Decreases

(c) Becomes unequal

(d) Remains constant

Mass of earth has been determined through

(a) Use of Kepler's  constancy law

(b) Sampling the density of earth's crust and using R

(c) Cavendish's determination of G and using R and 'g' at the surface

(d) Use of periods of satellites at different heights above earth's surface

In a circuit 5 percent of total current passes through a galvanometer.  If resistance of the galvanometer is G then value of the shunt is

(a) 19 G

(b) 20 G

(c)

(d)

A moving coil sensitive galvanometer gives at once much more deflection. To control its speed of deflection

(a) A high resistance is to be connected across its terminals

(b) A magnet should be placed near the coil

(c) A small copper wire should be connected across its terminals

(d) The body of galvanometer should be earthed

For a given temperature difference, which of the following pairs will generate maximum thermo e.m.f.

(a) Antimony-bismuth

(b) Silver-gold

(c) Iron-copper

(d) Lead-nickel

10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is

(a) 12.5 g

(b) 10.5 g

(c) 6.03 g

(d) 4.03 g

A 100 W bulb B₁, and two 60-W bulbs B₂ and B₃, are connected to a 250 V source, as shown in the figure. Now W₁, W₂ and W₃ are the output powers of the bulbs B₁, B₂ and B₃, respectively. Then

(a)

(b)

(c)

(d)