Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

The AC voltage across a resistance can be measured using:

1. A potentiometer.
2. A hot-wire voltmeter.
3. A moving-coil galvanometer.
4. A moving-magnet galvanometer.

The radius of hydrogen atom in its ground state is 5.3  . After collision with an electron it is found to have a radius of 21.2 . What is the principal quantum number n of the final state of the atom

(a) n = 4

(b) n = 2

(c) n = 16

(d) n = 3

In the given network capacitance,  and . What is the resultant capacitance between A and B

(a) 2.2 μF

(b) 3.2 μF

(c) 1.2 μF

(d) 4.7 μF

Photoelectric emission is observed from a metallic surface for frequencies  and  of the incident light rays (. If the maximum values of kinetic energy of the photoelectrons emitted in the two cases are in the ratio of 1 : k, then the threshold frequency of the metallic surface is

(a)

(b)

(c)

(d)

The field lines of a single positive charge are:

Assertion  :   The surface charge densities of two spherical conductors of different radii are equal. Then the electric field intensities near their surface are also equal.

Reason    : Surface charge density is equal to charge per unit area.

(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.

Which of the following is not a basic property of magnets.

In a transistor configuration b-parameter is

(a)

(b)

(c)

(d)

A very high magnetic field is applied to a stationary charge. Then the charge experiences

(a) A force in the direction of magnetic field

(b) A force perpendicular to the magnetic field

(c) A force in an arbitrary direction

(d) No force