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) ε0σ
(b) $$\frac{\sigma}{\varepsilon_{0}}$$
(c) $$\frac{\sigma}{2 \varepsilon_{0}}$$
(d) $$\frac{1}{2} \sigma \varepsilon_{0}$$
(c) $$\frac{\sigma}{2 \varepsilon_{0}}$$

Question 2.
Two capacitors C1 = 2µF and C2 = 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
(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) $$\frac{1}{\sqrt{2}}$$
(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
(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) $$\frac{1}{r^{3}}$$
(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
(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
(a) increase in temperature

Question 8.
The Drift velocity (vd) and applied electric field (E) of a conductor are related as:
(a) vd ∝√E
(b) vd ∝ E
(c) vd ∝ E2
(d) vd = Constant
(b) vd ∝ 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) $$q\{\vec{B}+(\vec{v} \times \vec{E})\}$$
(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
(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) $$\frac{1}{2} \mathrm{B} \mu_{0}^{2}$$
(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
(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
(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) $$\frac{2 \mathrm{M}}{\pi}$$
(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 = 6t2 – 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
(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
(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
(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
(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
(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)
(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″
(c) 1.5″

Question 22.
To remove the hyper ametropia lens used is :
(a) Convex
(b) Concave
(c) Cylindrical
(d) Plano-convex
(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
(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
(a) Total Internal reflection

Question 25.
The value of maximum amplitude produced due to interference of two waves is given by y1 = 4 sin wt and y2 = 3 cos wt
(a) 7
(b) 5
(c) 1
(d) 25
(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) $$\frac{2 \pi}{\lambda} \phi$$
(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) $$\frac{1}{2}$$
(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) $$\frac{m h}{\sqrt{2 q V}}$$
(c) $$\frac{h}{\sqrt{2 q m V}}$$

Question 29.
The number of Photons of frequency 1014 Hz in the radiation of 6.62J will be:
(a) 1010
(b) 1015
(c) 1020
(d) 1025
(c) 1020

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
(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
(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
(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
(b) Facsimile Telegraphy

Question 34.
A semiconductor is cooled from T1K to T2K, then its resistance will:
(a) increase
(b) decrease
(c) remain constant
(d) First, decrease then increase