Physics MCQ's - Gyanpoints

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Q.1 The error in measurement of radius of a sphere is 0.1% then error in its volume is –

(1) 0.3% (2) 0.4% (3) 0.5% (4) 0.6%

Q.2 A body starts falling from height ‘h’ and travels distance h/2 during last second of motion then time of flight is (In second) –

(1) $\displaystyle \sqrt{2}-1$

(2) $\displaystyle 2+\sqrt{2}$

(3) $\displaystyle \sqrt{2}+\sqrt{3}$

(4) $\displaystyle \sqrt{3}+2$

Q.3 The K.E. of a person is just half of K.E. of a boy whose mass is just half of that person. If person increases its speed by 1 m/s, then its K.E. equals to that of boy then initial speed of person was –

(1) $\displaystyle \left( {\sqrt{2}+1} \right)$ m/s

(2) $\displaystyle \left( {2+\sqrt{2}} \right)$ m/s

(3) $\displaystyle 2\left( {2+\sqrt{2}} \right)$ m/s

(4) None

Q.4 Two particles separated at a horizontal distance X as shown in fig. they projected at the same line as shown in fig. with different initial speeds. The time after which the horizontal distance between them become zero –

(1) $\displaystyle \frac{x}{u}$

(2) $\displaystyle \frac{u}{{2x}}$

(3) $\displaystyle \frac{{2u}}{x}$

(4) None of these

Q.5 For a particle displacement time relation is $\displaystyle t=\sqrt{x}+3$ . Its displacement when its velocity is zero –

(1) 2m

(2) 4m

(3) 0

(4) None of these

Q.6 If 100N force is applied to 10 kg. block as shown in diagram then acceleration produced for slab –

(1) 1.65 m/s²

(2) 0.98 m/s²

(3) 1.2 m/s²

(4) 0.25 m/s²

Q.7 The current in 8Ω resistance is (See fig.)

(1) 0.69 A

(2) 0.92 A

(3) 1.30 A

(4) 1.6 A

Q.8 The effective capacity of the network between terminals A and B is –

(1) 6 μF

(2) 20 μF

(3) 3 μF

(4) 10 μF

Q.9 If the power dissipated in 5Ω is 20 W then power dissipated in 4Ω is –

(1) 4 W (2) 6 W

(3) 10 W (4) 20 W

Q.10 The value of R for which power in it is maximum-

(1) 3Ω (2) 6Ω

(3) 12Ω (4) 9Ω

Q.11 Initially plane of coil is parallel to the uniform magnetic field B. In time Δt it makes to perpendicular to the magnetic field, then charge flows in Δt depends on this time as –

(1) ∝ Δt (2) ∝ $\displaystyle \frac{1}{{\Delta t}}$

(3) ∝ (Δt)⁰ (4) ∝ (Δt)²

Q.12 A current carrying coil (I = 5A, R = 10 cm.) having 50 number of turns find field at its centre-

(1) 1.57 mT (2) 3.14 mT

(3) 1 mT (4) 2 mT

Q.13 Eight equals charged tiny drops are combined to form a big drop. If the potential on each drop is 10V then potential of big drop will be –

(1) 40V (2) 10V

(3) 30V (4) 20V

Q.14 For a inductor coil L = 0.04 H, then work done by source to establish a current of 5A in it is –

(1) 0.5 J (2) 1.00 J

(3) 100 J (4) 20 J

Q.15 The terminal potential difference of a cell is greater than its emf when –

(1) A battery of less emf is connected in its series

(2) A battery of higher emf is connected in its series

(3) A battery of higher emf is connected in its parallel

(4) A battery of less emf is connected in its parallel

Q.16 In millikan oil drop experiment a charged drop falls with a terminal velocity V. If an electric field E is applied vertically upwards it moves with terminal velocity 2V in upward direction. If electric field reduces to E/2 then its terminal velocity will be –

(1) $\displaystyle \frac{V}{2}$

(2) V

(3) $\displaystyle \frac{{3V}}{2}$

(4) 2V

Q.17 For a vibration magnetometer, the time period of suspended bar magnet can be reduced by –

(1) Moving it towards south pole

(2) Moving it towards north pole

(3) Moving it towards equator

(4) Anyone of them

Q.18 The truth table for the following network is :

(1)

A	B	Y
0	0	0
0	1	0
1	0	0
1	1	1

(2)

A	B	Y
0	0	0
0	1	1
1	0	1
1	1	0

(3)

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	1

(4) None of the above

Q.19 Zener diode is used as –

(1) Half wave rectifier

(2) Full wave rectifier

(3) A.C. voltage stablizer

(4) D.C. voltage stablizer

Q.20 Depletion layer has (for an unbiased PN junction) –

(1) Electrons (2) Holes

(3) Static ions (4) Neutral atoms

Q.21 A cylindrical tube (L = 125 cm) is resonant with a tuning fork of frequency 330 Hz. If it is filling by water then to get resonance again, minimum

length of water column is (V_air = 330 m/s) –

(1) 50 cm (2) 60 cm (3) 25 cm (4) 20 cm

Q.22 Initial pressure and volume of a gas are P and V respectively. First its volume is expanded to 4V by isothermal process and then again its volume makes to be V by adiabatic process then its final pressure is (γ = 1.5) –

(1) 8P (2) 4P (3) P (4) 2P

Q.23 A sphere maintained at temperature 600 K, has cooling rate R in an external environment of 200 K temp. If its temp. falls to 400 K then its colling rate will be –

(1) $\displaystyle \frac{3}{{16}}$ R

(2) $\displaystyle \frac{{16}}{3}$ R

(3) $\displaystyle \frac{9}{{27}}$ R

(4) None

Q.24 A particle is projected with velocity ‘u’ makes an angle θ w.r.t. horizontal. Now it breaks in two identical parts at highest point of trajectory. If one part is retrace its path, then velocity of other part is –

(1) 3u cos θ (2) 2u cos θ

(3) u cos θ (4) u

Q.25 The amplitude of a S.H.O. reduces to 1/3 in first 20 secs. then in first 40 sec. its amplitude becomes –

(1) $\displaystyle \frac{1}{3}$

(2) $\displaystyle \frac{1}{9}$

(3) $\displaystyle \frac{1}{{27}}$

(4) $\displaystyle \frac{1}{{\sqrt{3}}}$

Q.26 Two springs A and B (K_A = 2 K_B) are stretched by same suspended weights then ratio of work done in stretching is –

(1) 1 : 2 (2) 2 : 1

(3) 1 : 1 (4) 1 : 4

Q.27 A spring elongated by length ‘L’ when a mass ‘M’ is suspended to it. Now a tiny mass ‘m’ is attached and then released, its time period of oscillation is –

(1) $\displaystyle 2\pi \sqrt{{\frac{{\left( {M+m} \right)l}}{{Mg}}}}$

(2) $\displaystyle 2\pi \sqrt{{\frac{{ml}}{{Mg}}}}$

(3) $\displaystyle 2\pi \sqrt{{\frac{L}{g}}}$

(4) $\displaystyle 2\pi \sqrt{{\frac{{Ml}}{{\left( {m+M} \right)g}}}}$

Q.28 Frequency of simple pendulum in a free falling lift is –

(1) Zero (2) Infinite

(3) Can’t be say (4) Finite

Q.29 The energy and capacity of a charged parallel plate capacitor are E and C respectively. Now a dielective slab of ∈_r = 6 is inserted in it then energy and capacity becomes (Assuming charge on plates remains constant)

(1) 6E, 6C (2) E, C

(3) $\displaystyle \frac{E}{6}$ , 6C

(4) E, 6C

Q.30 The current conduction in a discharge tube is due to –

(1) Electrons only

(2) +ve ions and –ve ions

(3) –ve ions and electrons

(4) +ve ions, and electrons

Q.31 A light of amplitude A and wavelength λ is incident on a metallic surface, then saturation current flows is proportional to (assume cut off wave length = λ₀) –

(1) A², if λ > λ₀ (2) A², if λ < λ₀

(3) A, if λ > λ₀ (4) A, if λ < λ₀

Q.32 Light of wavelength 3000 Å in Photoelectric effect gives electron of max. K.E. 0.5 eV. If wavelength change to 2000 Å then max. K.E. of emitted electrons will be :

(1) Less than 0.5 eV

(2) 0.5 eV

(3) Greater than 0.5 eV

(4) PEE does not occurs

Q.33 The K.E. of electron and photon is same then relation between their De-Broglie wavelength :

(1) λ_p < λ_e (2) λ_p = λ_e

(3) λ_p > λ_e (4) λ_p = 2λ_e

Q.34 The total energy of an electron is 3.555 MeV, then its Kinetic energy is :

(1) 3.545 MeV (2) 3.045 MeV

(3) 3.5 MeV (4) None

Q.35 Two identically charged particles A and B initially at rest, are accelerated by a common potential difference V. They enters into a transverse uniform magnetic field B. They describe a circular path of radii r₁ and r₂ respectively then their mass ratio is :

(1) $\displaystyle {{\left( {\frac{{{{r}_{1}}}}{{{{r}_{2}}}}} \right)}^{2}}$

(2) $\displaystyle {{\left( {\frac{{{{r}_{2}}}}{{{{r}_{1}}}}} \right)}^{2}}$

(3) $\displaystyle \left( {\frac{{{{r}_{1}}}}{{{{r}_{2}}}}} \right)$

(4) $\displaystyle \left( {\frac{{{{r}_{2}}}}{{{{r}_{1}}}}} \right)$

Q.36 A radio-active elements emits one α and β particles then mass no. of daughter element is :

(1) Decreased by 4 (2) Increased by 4

(3) Decreased by 2 (4) Increased by 2

Q.37 The half life of a radio nuclide is 77 days then its decay constant is :

(1) 0.003/day (2) 0.006/day

(3) 0.009/day (4) 0.012/day

Q.38 For a prism its refractive index is cot A/2 then minimum angle of deviation is :

(1) 180 – A (2) 180 – 2A

(3) 90 – A (4) A/2

Q.39 Two conducting slabs of heat conductivity K₁ and K₂ are joined as shown in fig. The temp. at ends of the slabs are θ₁ and θ₂ (θ₁ > θ₂) the, final temp. (θ_m) of junction is :

(1) $\displaystyle \frac{{{{K}_{1}}{{\theta }_{1}}+{{K}_{2}}{{\theta }_{2}}}}{{{{K}_{1}}+{{K}_{2}}}}$

(2) $\displaystyle \frac{{{{K}_{1}}{{\theta }_{2}}+{{K}_{2}}{{\theta }_{1}}}}{{{{K}_{1}}+{{K}_{2}}}}$

(3) $\displaystyle \frac{{{{K}_{1}}{{\theta }_{2}}-{{K}_{2}}{{\theta }_{1}}}}{{{{K}_{1}}+{{K}_{2}}}}$

(4) None

Q.40 A particle starts from rest with constant acceleration. The ratio of space-average velocity to the time average velocity is :

(1) $\displaystyle \frac{1}{2}$

(2) $\displaystyle \frac{3}{4}$

(3) $\displaystyle \frac{4}{3}$

(4) $\displaystyle \frac{3}{2}$

Q.41 If radius of earth shrinks by 1% then for acceleration due to gravity :

(1) No change at poles

(2) No change at equator

(3) Max. change at equator

(4) Equal change at all locations

Q.42 Rohini satellite is at a height of 500 km. and Insat-B is at a height of 3600 km. from surface of earth then relation between their orbital velocity (V_R,V_I) is :

(1) V_R > V₁ (2) V_R < V₁

(3) V_R = V₁ (4) No relation

Q.43 For moon, its mass is 1/81 of earth mass and its diameter is 1/3.7 of earth dia. If acceleration due to gravity at earth surface is 9.8 m/s2 then at moon its value is :

(1) 2.86 m/s² (2) 1.65 m/s²

(3) 8.65 m/s² (4) 5.16 m/s²

Q.44 When a spring is subjected to 4N force its length is a metre and if 5N is applied length is b metre. If 9N is applied its length is :

(1) 4b – 3a (2) 5b – a

(3) 5b – 4a (4) 5b – 2a

Q.45 For a body angular velocity $\displaystyle \overrightarrow{\omega }=\widehat{i}-\widehat{j}+3\widehat{k}$ and radius vector is $\displaystyle \overrightarrow{r}=\widehat{i}+\widehat{j}+\widehat{k}$ then its

velocity is :

(1) $\displaystyle -5\widehat{i}+2\widehat{j}+3\widehat{k}$

(2) $\displaystyle -5\widehat{i}+2\widehat{j}-3\widehat{k}$

(3) $\displaystyle -5\widehat{i}-2\widehat{j}+3\widehat{k}$

(4) $\displaystyle -5\widehat{i}-2\widehat{j}-3\widehat{k}$

Q.46 When a stick is released (as shown in fig.). Its free end velocity when it strikes the ground is :

(1) 4.2 m/s (2) 1.4 m/s

(3) 2.8 m/s (4) $\displaystyle \sqrt{6}$ m/s

Q.47 Frequency of an E.M. waves is 10 MHz then its wavelength is :

(1) 30 m (2) 300 m

(3) 3 m (4) None of the above

Q.48 Two particles are projected with same initial velocity one makes angle θ with horizontal while other makes an angle θ with vertical. If their common range is R then product of their time of flight is directly proportional to :

(1) R (2) R² (3) $\displaystyle \frac{1}{R}$ (4) R⁰

Q.49 In compound microscope the magnification is 95, and the distance of object from objective lens 1/3.8 cm and focal length of objective is ¼ cm. What is the magnification of eye pieces when final image is formed at least distance of distinct vision :

(1) 5 (2) 10 (3) 100 (4) None

Q.50 On the basis of unit cell concept a crystal has :

(1) 7 systems (2) 14 systems

(3) 230 systems (4) 32 systems

Physics MCQ’s

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