Atoms — Physics STD 12 Science — Question

Ionization energy of a hydrogen-like ion A is greater than that of another hydrogen-like ion B. Let r, u, E and L represent the radius of the orbit, speed of the electron, energy of the atom and orbital angular momentum of the electron respectively. In ground state:

The narrowest hysterisis loop is for:

The length of the compound microscope is 14 cm. The magnifying power for relaxed eye is 25. If the focal length of eye lens is 5 cm, then the object distance for objective lens will be

(a) 1.8 cm

(b)  1.5 cm

(c) 2.1 cm

(d)  2.4 cm

In the circuit shown here  and battery B = 20V. The switch  is first closed. It is then opened and afterwards   is closed. What is the charge finally on

(a) 120 μC

(b) 80 μC

(c) 40 μC

(d) 20 μC

Chadwick was awarded the Nobel Prize in Physics in 1935 for his discovery of:

The electric field between the two spheres of a charged spherical condenser

(a) Is zero	(b) Is constant
(c) Increases with distance from the centre	(d) Decreases with distance from the centre

A string of negligible thickness is wrapped several times around a cylinder kept on a rough horizontal surface. A man standing at a distance 1 from the cylinder holds one end of the string and pulls the cylinder towards him. There is no slipping anywhere. The length of the string passed through the hand of the man while the cylinder reaches his hands is:

1. l
2. 2l
3. 3l
4. 4l

In a P-type semiconductor, germanium is doped with

(a) Boron

(b) Gallium

(c) Aluminium

(d) All of these

A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then

(a)  A current will be induced in a coil

(b)  No current will be induced in a coil

(c)  Only an e.m.f. will be induced in the coil

(d)  An e.m.f. and a current both will be induced in the coil

What is the current (i) in the circuit as shown in figure

(a) 2 A

(b) 1.2 A

(c) 1 A

(d) 0.5 A