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) \(\frac{1}{2} \sigma \varepsilon_{0}\)
Answer:
(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
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 (vd) and applied electric field (E) of a conductor are related as:
(a) vd ∝√E
(b) vd ∝ E
(c) vd ∝ E2
(d) vd = Constant
Answer:
(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) \(q\{\vec{B}+(\vec{v} \times \vec{E})\}\)
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 = 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
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 y1 = 4 sin wt and y2 = 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 1014 Hz in the radiation of 6.62J will be:
(a) 1010
(b) 1015
(c) 1020
(d) 1025
Answer:
(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
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 T1K to T2K, 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
