Atoms — Physics STD 12 Science — Question

What is the use of a Van de Graff generator?

Binding energy per nucleon plot against the mass number for stable nuclei is shown in the figure. Which curve is correct

(a) A

(b) B

(c) C

(d) D

Which of the following cannot be used in electronic devices?

The current in a LR circuit builds up to  th of its steady state value in 4s. The time constant of this circuit is

(a)

(b)

(c)

(d)

The unit of magnetic moment is

(a) Wb/m

(b)

(c) A.m

(d)

A girl brings a positively charged rod near a thin neutral stream of water flowing from a tap. She observes, that the water stream, bends towards her. Instead, if she is to bring a negativity charged rod near to the stream, it will:

The stopping potential (  versus frequency (n) plot of a substance is shown in figure the threshold wave length is

(a) 5	(b) 6000Å
(c) 5000 Å	(d) Can not be estimated from given data

Two protons are kept at a separation of 10nm. Let F_n and F_e be the nuclear force and the electromagnetic force between them:

1. F_e = F_n.
   
2. F_e >> F_n.
   
3. F_e << F_n.
   
4. F_e and F_n differ only slightly.
   

Electrically, photons are:

Assertion  :   Torque on the coil is the maximum, when coil is suspended in a radial magnetic field.

Reason      : The torque tends to rotate the coil on its own axis.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.