Atoms — Physics STD 12 Science — Question

Molybdenum is used as a target element for production of X-rays because it is

(a) A heavy element and can easily absorb high velocity electrons

(b) A heavy element with a high melting point

(c) An element having high thermal conductivity

(d) Heavy and can easily deflect electrons

Hydrogen atoms are excited from ground state of the principal quantum number 4. Then the number of spectral lines observed will be

(a) 3

(b) 6

(c) 5

(d) 2

Energy conversion in a photoelectric cell takes place from

(a) Chemical to electrical	(b) Magnetic to electrical
(c) Optical to electrical	(d) Mechanical to electrical

Identify the direction in which a thin long piece of magnet comes to rest when suspended freely.

As the mass number A increases, which of the following quantities related to a nucleus do not change?

1. Mass.
2. Volume.
3. Density.
4. Binding energy.

A capacitor of capacity  is charged to the potential of . On disconnecting with the battery, it is connected with a capacitor of capacity   as shown in the adjoining figure. The ratio of energies before and after the connection of switch  S will be

(a) (

(b)

(c)

(d)

A beam consisting of protons and electrons moving at the same speed goes through a thin region in which there is a magnetic field perpendicular to the beam. The protons and the electrons:

1. Will go undeviated.
2. Will be deviated by the same angle and will not separate.
3. Will be deviated by different angles and hence separate.
4. Will be deviated by the same angle but will separate.

If you are provided three resistances 2 W, 3 W and 6 W. How will you connect them so as to obtain the equivalent resistance of 4 W

(a)

(b)

(c)

(d) None of these

What is the coefficient of mutual inductance when the magnetic flux changes by 2   and change in current is 0.01A

(a) 2 henry

(b) 3 henry

(c)  henry

(d) Zero