Atoms — Physics STD 12 Science — Question

In a hydrogen atom, an electron moves in a circular orbit of radius 5.2   and produces a magnetic induction of 12.56 T at its nucleus. The current produced by the motion of the electron will be (Given  

(a) 6.53	(b) 13.25
(c) 9.6	(d) 1.04

A person sitting firmly over a rotating stool has his arms stretched. If he folds his arms, his angular momentum about the axis of rotation:

1. Increases.
2. Decreases.
3. Remains unchanged.
4. Doubles.

Two resistances are joined in parallel whose resultant is  ohm. One of the resistance wire is broken and the effective resistance becomes 2Ω. Then the resistance in ohm of the wire that got broken was

(a) 3/5

(b) 2

(c) 6/5

(d) 3

An electron revolves 6 × 10¹⁵ times/sec in circular loop.  The current in the loop is

(a) 0.96 mA

(b) 0.96 m A

(c) 28.8 A

(d) None of these

The best suitable metal for photoelectric effect is:

A wave moving in a gas,

1. Must be longitudinal
2. May be longitudinal
3. Must be transverse
4. May be transverse

Which of the following effects could not be explained by Maxwell's electromagnetic wave theory?

In a Young's double slit experiment, the central point on the screen is

(a) Bright	(b) Dark
(c) First bright and then dark	(d) First dark and then bright

An electric heating element in vacuum is surrounded by a cavity at constant temperature of 227ºC; it consumes 60W of power to maintain a temperature of 727ºC. What is the power consumed by the element to maintain a temperature of 1227º C?

If E and B represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of electromagnetic wave is along,