Magnetism and Matter — Physics STD 12 Science — Question

Forty electric bulbs are connected in series across a 220 V supply. After one bulb is fused, the remaining 39 are connected again in series across the same supply. The illumination will be

(a) More with 40 bulbs than with 39	(b) More with 39 bulbs than with 40
(c) Equal in both the cases	(d) In the ratio of

If Young's double slit experiment is performed in water:

1. The fringe width will decrease.
2. The fringe width will increase.
3. The fringe width will remain unchanged.
4. There will be no fringe.

Field inside a solenoid is

(a) Directly proportional to its length

(b) Directly proportional to current

(c) Inversely proportional to total number of turns

(d) Inversely proportional to current

In the circuit shown in figure, the current drawn from the battery is 4A.  If 10 W resistor is replaced by 20 W resistor, then current drawn from the circuit will be

(a) 1 A

(b) 2 A

(c) 3 A

(d) 0 A

If length of a conductor is doubled and cross-section is made half, then the specific resistance of the substance of changed wire will become:

Two resistors having equal resistances are joined in series and a current is passed through the combination. Neglect any variation in resistance as the temperature changes. In a given time interval

(a) Equal amounts of thermal energy must be produced in the resistors

(b) Unequal amounts of thermal energy may be produced

(c) The temperature must rise equally in the resistors

(d) The temperature must rise unequally in the resistors

A hydrogen atom (ionisation potential 13.6 eV) makes a transition from third excited state to first excited state. The energy of the photon emitted in the process is

(a) 1.89 eV

(b) 2.55 eV

(c) 12.09 eV

(d) 12.75 eV

The refractive index of water is 4 / 3 and that of glass is 5/3.  What will be the critical angle for the ray of light entering water from the glass  

(a)

(b)

(c)

(d)

The materials suitable for making electromagnets should have: