Bihar Board 12th Physics Objective Questions and Answers

## Bihar Board 12th Physics VVI Objective Questions Model Set 1 in English

Question 1.

The electric Held at a point near an infinite thin sheet of charged conductor is:

(a) ε_{0}σ

(b) \(\frac{\sigma}{\varepsilon_{0}}\)

(c) \(\frac{\sigma}{2 \varepsilon_{0}}\)

(d) \(\frac{1}{2} \sigma \varepsilon_{0}\)

Answer:

(c) \(\frac{\sigma}{2 \varepsilon_{0}}\)

Question 2.

Two capacitors C_{1} = 2µF and C_{2} = 4µF are connected in series and a potential difference (p.d.) of 1200 V is applied across it. The Potential difference across 2µF will be:

(a) 400 V

(b) 600 V

(c) 800 V

(d) 900V

Answer:

(c) 800 V

Question 3.

In the figure, if net force on Q is zero then value of \(\frac{\mathrm{Q}}{\mathrm{q}}\) is:

(a) √2

(b) 2√2

(c) \(\frac{1}{2 \sqrt{2}}\)

(d) \(\frac{1}{\sqrt{2}}\)

Answer:

(b) 2√2

Question 4.

When a body is charged, it’s mass

(a) increases

(b) decreases

(c) remains the same

(d) may increase or decrease

Answer:

(d) may increase or decrease

Question 5.

The electric potential due to a small electric dipole at a large distance r from the center of the dipole is proportional to:

(a) r

(b) \(\frac{1}{r}\)

(c) \(\frac{1}{r^{2}}\)

(d) \(\frac{1}{r^{3}}\)

Answer:

(c) \(\frac{1}{r^{2}}\)

Question 6.

Minimum number of capacitors of 2µF each required to obtain a capacitance of 5µF will be

(a) 4

(b) 3

(c) 5

(d) 6

Answer:

(a) 4

Question 7.

The specific resistance of the conductor increases with:

(a) increase in temperature

(b) increase of cross-sectional area

(c) decrease in length

(d) decrease of the cross-sectional area

Answer:

(a) increase in temperature

Question 8.

The Drift velocity (v_{d}) and applied electric field (E) of a conductor are related as:

(a) v_{d} ∝√E

(b) v_{d} ∝ E

(c) v_{d} ∝ E^{2}

(d) v_{d} = Constant

Answer:

(b) v_{d} ∝ E

Question 9.

A charge ‘q’ moves in a region where electric field ‘E’ and magnetic field ‘B’ both exist, then force on it is:

(a) \(q(\vec{v} \times \vec{B})\)

(b) \(\mathrm{q} \overrightarrow{\mathrm{E}}\)

(c) \(q\{\vec{E}+(\vec{v} \times \vec{B})\}\)

(d) \(q\{\vec{B}+(\vec{v} \times \vec{E})\}\)

Answer:

(b) \(\mathrm{q} \overrightarrow{\mathrm{E}}\)

Question 10.

A bar magnet of magnetic moment M is cut into two parts of equal length. The magnetic moment of either part is :

(a) M

(b) \(\frac {M}{2}\)

(c) 2M

(d) Zero

Answer:

(b) \(\frac {M}{2}\)

Question 11.

The dimensional formula for \(\frac{1}{2} \varepsilon_{0} \mathbf{E}^{2}\) is identical to that of:

(a) \(\frac{\mathrm{B}^{2}}{2 \mu_{0}}\)

(b) \(\frac{1}{2} B^{2} \mu_{0}\)

(c) \(\frac{\mu_{0}^{2}}{2 \mathrm{B}}\)

(d) \(\frac{1}{2} \mathrm{B} \mu_{0}^{2}\)

Answer:

(a) \(\frac{\mathrm{B}^{2}}{2 \mu_{0}}\)

Question 12.

A circular coil of radius R carries a current I. The magnetic field at its centre is B. At what distance from the centre, on the axis of the coil, the magnetic field will be B/8.

(a) √2R

(b) 2R

(c) √3R

(d) 3R

Answer:

(c) √3R

Question 13.

The magnetic dipole moment is a vector quantity directed from:

(a) South to the North Pole

(b) North to the South Pole

(c) East to West direction

(d) West to East direction

Answer:

(a) South to the North Pole

Question 14.

A wire of magnetic dipole moment M and L is bent into shape of a semicircle of radius r. What will be its new dipole moment?

(a) M

(b) \(\frac{\mathrm{M}}{2 \pi}\)

(c) \(\frac{\mathrm{M}}{\pi}\)

(d) \(\frac{2 \mathrm{M}}{\pi}\)

Answer:

(d) \(\frac{2 \mathrm{M}}{\pi}\)

Question 15.

In a closed circuit of resistance 10W, the linked flux varies with time according to relation Φ = 6t^{2} – 5t + 1. At t = 0.25 second, the current (in Ampere) flowing through the circuit is:

(a) 0.4

(b) 0.2

(c) 2.0

(d) 4.0

Answer:

(b) 0.2

Question 16.

In A.C. circuit, the current and voltage are given by i = 5 cos wt, and V = 200 sin wt respectively. Power loss in the circuit is:

(a) 20 W

(b) 40W

(c) 1000W

(d) zero

Answer:

(d) zero

Question 17.

The energy of electromagnetic radiation is 13.2 keV. This radiation is related to which region of the spectrum?

(a) Visible

(b) X-rays

(c) Ultraviolet

(d) Infrared

Answer:

(b) X-rays

Question 18.

The image formed by the objective lens of a compound Microscope is:

(a) Virtual and diminished

(b) Real and diminished

(c) Real and large

(d) Virtual and Large

Answer:

(c) Real and large

Question 19.

A convex lens is dipped in a liquid, whose refractive index is equal to the refractive index of the material of the lens. Then its focal length will:

(a) become zero

(b) become infinite

(c) decrease

(d) increase

Answer:

(b) become infinite

Question 20.

Critical angle for light moving from medium I to medium II is θ. The speed of light in medium I is v. Then speed in medium II is :

(a) v(1 – cosθ)

(b) \(\frac{v}{\sin \theta}\)

(c) \(\frac{v}{\cos \theta}\)

(d) v(1 – sinθ)

Answer:

(b) \(\frac{v}{\sin \theta}\)

Question 21.

A magnifying glass is to be used at the fixed object distance of 1 inch. If it is to produce an erect image 5 items magnified, its focal length should be :

(a) 0.2″

(b) 0.8″

(c) 1.5″

(d) 5″

Answer:

(c) 1.5″

Question 22.

To remove the hyper ametropia lens used is :

(a) Convex

(b) Concave

(c) Cylindrical

(d) Plano-convex

Answer:

(a) Convex

Question 23.

Which of the following phenomena taken place when monochromatic light is incident on a prism?

(a) Dispersion

(b) Deviation

(c) Interference

(d) All of the above

Answer:

(a) Dispersion

Question 24.

Optical fibre communication is based on which of the following phenomena:

(a) Total Internal reflection

(b) Scattering

(c) Reflection

(d) Interference

Answer:

(a) Total Internal reflection

Question 25.

The value of maximum amplitude produced due to interference of two waves is given by y_{1} = 4 sin wt and y_{2} = 3 cos wt

(a) 7

(b) 5

(c) 1

(d) 25

Answer:

(b) 5

Question 26.

The phase difference Φ is related to Path difference Δx by:

(a) \(\frac{\lambda}{\pi} \phi\)

(b) \(\frac{\pi}{\lambda}\)

(c) \(\frac{\lambda}{2 \pi} \phi\)

(d) \(\frac{2 \pi}{\lambda} \phi\)

Answer:

(c) \(\frac{\lambda}{2 \pi} \phi\)

Question 27.

The resolving power of human eye (in minute) is :

(a) \(\frac{1}{60}\)

(b) 1

(c) 10

(d) \(\frac{1}{2}\)

Answer:

(a) \(\frac{1}{60}\)

Question 28.

A particle of mass m and charged q is accelerated through a potential V. The De-Broglie wavelength of the particle will be:

(a) \(\frac{V h}{\sqrt{2 q m}}\)

(b) \(\frac{q}{\sqrt{2 m V}}\)

(c) \(\frac{h}{\sqrt{2 q m V}}\)

(d) \(\frac{m h}{\sqrt{2 q V}}\)

Answer:

(c) \(\frac{h}{\sqrt{2 q m V}}\)

Question 29.

The number of Photons of frequency 10^{14} Hz in the radiation of 6.62J will be:

(a) 10^{10}

(b) 10^{15}

(c) 10^{20}

(d) 10^{25}

Answer:

(c) 10^{20}

Question 30.

The minimum angular momentum of electron in hydrogen atom will be:

(a) \(\frac{h}{\pi}\) Js

(b) \(\frac{h}{2 \pi}\) Js

(c) hπ Js

(d) 2πh Js

Answer:

(b) \(\frac{h}{2 \pi}\) Js

Question 31.

The atomic number and mass number for a specimen are Z and A respectively. The number of neutrons in the atom will be :

(a) A

(b) Z

(c) A + Z

(d) A – Z

Answer:

(d) A – Z

Question 32.

The quantities, which remain conserved in a nuclear reaction:

(a) Total Charge

(b) Angular momentum

(c) Linear momentum

(d) All the above

Answer:

(d) All the above

Question 33.

Meaning of “FAX” is :

(a) Full Access Transmission

(b) Facsimile Telegraphy

(c) Factual Auto Access

(d) Feed Auto Exchange

Answer:

(b) Facsimile Telegraphy

Question 34.

A semiconductor is cooled from T_{1}K to T_{2}K, then its resistance will:

(a) increase

(b) decrease

(c) remain constant

(d) First, decrease then increase

Answer:

(a) increase

Question 35.

If the current constant for a transistor are α & β then:

(a) αβ = 1

(b) β > 1, α < 1

(c) α = β

(d) β < 1, α > 1

Answer:

(b) β > 1, α < 1