Semiconductor Electronics: Materials, Devices and Simple Circuits — Physics STD 12 Science — Question

Electric field intensity at a point in between two parallel sheets with like charges of same surface charge densities (σ)  is

(a)

(b)

(c) Zero

(d)

A wire in the form of a square of side ‘a’ carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space =

(a)

(b)

(c)

(d)

A circular disc is placed in front of a narrow source. When the point of observation is at a distance of 1 meter from the disc, then the disc covers first HPZ. The intensity at this point is I₀. The intensity at a point distance 25 cm from the disc will be

(a)

(b)

(c)

(d)

If flux of the electric field through a closed surface is zero:

1. The electric field must be zero everywhere on the surface.
2. The electric field may be zero everywhere in the surface.
3. The charge inside the surface must be zero.
4. The charge in the vicinity of the surface must be zero.

An electric dipole has the magnitude of its charge as q and its dipole moment is p. It is placed in a uniform electric field E. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively

(a) 2q.E and minimum

(b) q.E  and p.E

(c) Zero and minimum

(d) q.E and maximum

The two ends of a spring are displaced along the length of the spring. All displacement have equal magnitudes. In which case or cases the tension or compression in the spring will have a maximum magnitude?

1. The right end is displaced towards right and the left end towards left.
2. Both ends are displaced towards right.
3. Both ends are displaced towards left.
4. The right end is displaced towards left and the left end towards right.

Photoelectric emmision occurs only when the incident light has more than a certain minimum?

A nucleus of atomic mass A and atomic number Z emits β - particles. The atomic mass and atomic number of the resulting nucleus are

(a) A, Z

(b) A + 1, Z

(c) A, Z + 1

(d) A – 4, Z - 2

Capacitance (in F) of a spherical conductor with radius 1m is

(a) 1.1

(b)

(c) 9 ×

(d)

Assertion  :  A transistor amplifier in common emitter configuration has a low input impedence.

Reason      : The base to emitter region is forward biased.

(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.