Physics MCQ's - Gyanpoints

Q.1 Boron has two isotopes ₅B¹⁰ and ₅B¹¹. If atomic weight of Boron is 10.81 then ratio of ₅B¹⁰ to ₅B¹¹ in nature will be :

(1) 15 : 16 (2) 19 : 81

(3) 81 : 19 (4) 20 : 53

Q.2 A hollow sphere of radius 1m is given a positive charge of 10μC. The electric field at the centre of hollow sphere will be :

(1) 60 × 10³ Vm^–1 (2) 90 × 10³ Vm^–1

(3) Zero (4) Infinite

Q.3 Following table is for which logic gate :

Input		Output
A	B	C
0	0	1
0	1	1
1	0	1
1	1	0

(1) AND (2) OR

(3) NAND (4) NOT

Q.4 Following logic gate is :

(1) AND (2) NAND

(3) EX-OR (4) OR

Q.5 For a wave y = y₀sin (ωt – kx), for what value of λ is the maximum particle velocity equal to two times the wave velocity :

(1) πy₀ (2) 2πy₀

(3) πy₀/2 (4) 4πy₀

Q.6 Two pendulums suspended from same point having length 2m and 0.5m. If they displaced slightly and released then they will be in same phase, when small pendulum will have completed:

(1) 2 oscillation (2) 4 oscillation

(3) 3 oscillation (4) 5 oscillation

Q.7 For protecting a magnetic needle it should be placed :

(1) In iron box (2) In wooden box

(3) In metallic box (4) None of these

Q.8 A circular ring of mass M and radius R is rotating about its axis with constant angular velocity ω. Two particle each of mass m are attached gently to the opposite ends of a diameter of the ting. The angular velocity of the ring will now become :

(1) $\displaystyle \frac{{m\omega }}{{M+2m}}$

(2) $\displaystyle \frac{{M\omega }}{{M-2m}}$

(3) $\displaystyle \frac{{M\omega }}{{M+2m}}$

(4) $\displaystyle \frac{{M+2m}}{{M\omega }}$

Q.9 If x = 3 – 4t² + t³, then work done in first 4s. will be (Mass of the particle is 3 gram) :

(1) 384 mJ (2) 168 mJ

(3) 192 mJ (4) None of these

Q.10 If force F = 500 – 100t, then function of impulse with time will be :

(1) 500t – 50t² (2) 50t – 10

(3) 50 – t² (4) 100 t²

Q.11 Half life period of two elements are 40 minute and 20 minute respectively, then after 80 minute ratio of the remaining nuclei will be (Initially both have equal active nuclei) :

(1) 4 : 1 (2) 1 : 2 (3) 8 : 1 (4) 16 : 1

Q.12 A particle of mass m is tied to a string of length L and whirled into a horizontal plan. If tension in the string is T then the speed of the particle

will be :

(1) $\displaystyle \sqrt{{\frac{{Tl}}{m}}}$

(2) $\displaystyle \sqrt{{\frac{{2Tl}}{m}}}$

(3) $\displaystyle \sqrt{{\frac{{3Tl}}{m}}}$

(4) $\displaystyle \sqrt{{\frac{T}{{ml}}}}$

Q.13 If the light of wavelength λ is incident on metal surface, the ejected fastest electron has speed v. If the wavelength is changed to $\displaystyle \frac{{3\lambda }}{4}$ speed of the fastest emitted electron will be :

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

(2) Greater than $\displaystyle \sqrt{{\frac{4}{3}}}$ v

(3) 2v

(4) Zero

Q.14 A coil of one loop is made from a wire of length L and thereafter a coil of two loops is made from same wire, then the ratio of magnetic field at the centre of coils will be :

(1) 1 : 4 (2) 1 : 1

(3) 1 : 8 (4) 4 : 1

Q.15 The speed of a boat is 5 km/hr is still water. It crosses a river of width 1 km along the shortest possible path in 15 minutes. The velocity of river water is :

(1) 3 km/hr (2) 4 km/hr

(3) 5 km/hr (4) 2 km/hr

Q.16 Two identical balls A and B are moving with velocity +0.5 ms^–1 and – 0.3 ms^–1 respectively. They collide head on elastically then their velocities after collision will be :

(1) – 0.3 ms^–1 & 0.5 ms^–1

(2) + 0.5 ms^–1 & + 0.3 ms^–1

(3) –0.4 ms^–1 & 0.3 ms^–1

(4) 0.3 ms^–1 & – 0.4 ms^–1

Q.17 A small ball is suspended from a thread. It is lifted up with an acceleration 4.9 ms^–2 and lowered with an acceleration 4.9 ms^–2 then the ratio of tensions in the thread in both cases will be :

(1) 1 : 3 (2) 3 : 1

(3) 1 : 1 (4) 1 : $\displaystyle \sqrt{5}$

Q.18 One part of a device is connected with the negative terminal of a battery and another part is connected with the positive terminal of a battery. If their ends now altered, current does not flow in circuit, then the device will be :

(1) P–N Junction (2) Transistor

(3) Zener diode (4) Triode

Q.19 Light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index of the material of the rod, the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence :

(1) n > $\displaystyle \sqrt{2}$ (2) 1.0

(3) 1.3 (4) 1.4

Q.20 10⁵ coloumb charge liberated 1 gm silver (Ag). If now charge is doubled then the amount of liberated Ag will be :

(1) 1 gm (2) 2 gm (3) 3 gm (4) 4 gm

Q.21 Work function of a metal surface is φ = 1.5 eV. If a light of wavelength 5000Å falls on it then the maximum K.E. of ejected electron will be –

(1) 1.2 eV (2) 0.98 eV

(3) 0.45 eV (4) 0 eV

Q.22 If time of mean position from amplitude (extreme) position is 6 s. then the frequency of SHM will be :

(1) 0.01 Hz (2) 0.02 Hz

(3) 0.03 Hz (4) 0.04 Hz

Q.23 Two coil have a mutual inductance 0.005 H. The current changes in first coil according to equation I = I₀ sin ωt where I₀ = 2A and ω = 100π rad/sec. The maximum value of emf in second coil is :

(1) 4π (2) 3π

(3) 2π (4) π

Q.24 Resistance of a Galvanometer coil is 8Ω and 2Ω Shunt resistance is connected with it. If main current is 1 A then the current flow through 2Ω

resistance will be :

(1) 0.2 A (2) 0.8 A

(3) 0.1 A (4) 0.4 A

Q.25 If a ladder is not in balance against a smooth vertical wall, then it can be made in balance by :

(1) Decreasing the length of ladder

(2) Increasing the length of ladder

(3) Increasing the angle of inclination

(4) Decreasing the angle of inclination

Q.26 For a Rocket propulsion velocity of exhaust gases relative to rocket is 2 km/s. If mass of rocket system is 1000 kg, then the rate of fuel consumption for a rocket to rise up with acceleration 4.9 m/s² will be :

(1) 12.25 kg/s (2) 17.5 kg/s

(3) 7.35 kg/s (4) 5.2 kg/s

Q.27 O is the centre of an equilateral triangle ABC $\displaystyle \overrightarrow{{{{F}_{1}}}}$ , $\displaystyle \overrightarrow{{{{F}_{2}}}}$ , $\displaystyle \overrightarrow{{{{F}_{3}}}}$ are three forces acting along the sides AB, BC and AC as shown in fig. What should be the magnitude of $\displaystyle \overrightarrow{{{{F}_{3}}}}$ so that total torque about O is zero :

(1) $\displaystyle \left| {\overrightarrow{{{{F}_{3}}}}} \right|=\left| {\overrightarrow{{{{F}_{1}}}}} \right|+\left| {\overrightarrow{{{{F}_{2}}}}} \right|$

(2) $\displaystyle \left| {\overrightarrow{{{{F}_{3}}}}} \right|=\left| {\overrightarrow{{{{F}_{1}}}}} \right|-\left| {\overrightarrow{{{{F}_{2}}}}} \right|$

(3) $\displaystyle \left| {\overrightarrow{{{{F}_{3}}}}} \right|=\overrightarrow{{{{F}_{1}}}}-2\overrightarrow{{{{F}_{2}}}}$

(4) Not possible

Q.28 When volume changes from V to 2V at constant pressure(P) then the change in internal energy will be :

(1) PV (2) 3PV (3) $\displaystyle \frac{{PV}}{{\gamma -1}}$

(4) $\displaystyle \frac{{RV}}{{\gamma -1}}$

Q.29 A gas of volume changes 2 litre to 10 litre at constant temperature 300K, then the change in internal energy will be :

(1) 12 J (2) 24 J (3) 36 J (4) 0 J

Q.30 When three identical bulbs are connected in series, the consumed power is 10W. If they are now connected in parallel then the consumed power will be :

(1) 30W (2) 90W (3) $\displaystyle \frac{{10}}{3}$ W (4) 270W

Q.31 A ball is dropped from a height of 5 m, if it rebound upto height of 1.8 m, then the ratio of velocities of the ball after and before rebound is :

(1) $\displaystyle \frac{3}{5}$

(2) $\displaystyle \frac{2}{5}$

(3) $\displaystyle \frac{1}{5}$

(4) $\displaystyle \frac{4}{5}$

Q.32 Two long parallel wires are at a distance of 1m. If both of them carry one ampere of current in same direction, then the force of attraction on unit length of the wires will be :

(1) 2 × 10^–7 N/m (2) 4 × 10^–7 N/m

(3) 8 × 10^–7 N/m (4) 10^–7 N/m

Q.33 For the diffraction from a crystal with λ = 1Å and Bragg’s angle θ = 60°, then for the second order diffraction ‘d’ will be :

(1) 1.15 Å (2) 0.75 Å

(3) 0.55 Å (4) 2.1 Å

Q.34 If the frequency of a spring is n after suspending mass M, now 4M mass is suspended from spring then the frequency will be :

(1) 2n (2) n/2

(3) n (4) None of the above

Q.35 A standing wave having 3 nodes and 2 antinodes is formed between 1.21 Å distance then the wavelength is :

(1) 1.21 Å (2) 2.42 Å

(3) 0.605 Å (4) 4.84 Å

Q.36 In hot wire Ammeter due to flowing of current temperature of wire is increased by 5°C. If value of current is doubled, then increases in temperature will be :

(1) 15°C (2) 20°C

(3) 25°C (4) 30°C

Q.37 A car is moving with velocity V. If stop after applying break at a distance of 20 m. If velocity of car is doubled, then how much distance it will cover (travel) after applying break :

(1) 40 m (2) 80 m (3) 160 m (4) 320 m

Q.38 A charge q is placed in an uniform electric field E. If it is released, then the K.E of the charge after travelling distance y will be :

(1) qEy (2) 2qEy

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

(4) $\displaystyle \sqrt{{qEy}}$

Q.39 In the Bohr model of H-atom, an electron (e) is revolving around a proton (p) with velocity v, if r is the radius of orbit and m is mass and ε₀ is vacuum permittivity, the value of v is :

(1) $\displaystyle \frac{e}{{\sqrt{{4\pi m{{\in }_{0}}r}}}}$

(2) $\displaystyle \frac{{2e}}{{\sqrt{{4\pi m{{\in }_{0}}r}}}}$

(3) $\displaystyle \frac{e}{{\sqrt{{\pi m{{\in }_{0}}r}}}}$

(4) $\displaystyle \frac{e}{{\sqrt{{4\pi m{{\in }_{0}}r}}}}$

Q.40 Electric field at the equator of a dipole is E. If strength and distance is now doubled then the electric field will be :

(1) E/2 (2) E/8 (3) E/4 (4) E

Q.41 Turn ratio of a step-up transformer is 1 : 25. If current in load coil is 2A, then the current in primary coil will be :

(1) 25A (2) 50A (3) 0.25A (4) 0.5A

Q.42 If a source moves perpendicularly from listener then the change in frequency will be :

(1) 2 n (2) n (3) n/2 (4) Zero

Q.43 for nuclear reaction : ₉₂U²³⁵ + ₀n¹ → ₅₆Ba¹⁴⁴ + ………. + 3₀n¹

(1) ₂₆Kr⁸⁹ (2) ₃₆Kr⁸⁹

(3) ₂₆Sr⁹⁰ (4) ₃₈Sr⁸⁹

Q.44 A rigid rod is placed against the wall as shown in figure. When its velocity of lower end is 10 ms^–1 and its base makes an angle α = 60° with horizontal, then the vertical velocity of its end B will be :

(1) 10 $\displaystyle \sqrt{3}$ (2) $\displaystyle \frac{{10}}{{\sqrt{3}}}$ (3) 5 $\displaystyle {\sqrt{3}}$ (4) $\displaystyle \frac{5}{{\sqrt{3}}}$

Q.45 Radiation energy corresponding to the temperature T of the sun is E. If its temperature is doubled, then its radiation energy will be :

(1) 32 E (2) 16 E (3) 8 E (4) 4 E

Q.46 The cause of potential barrier in a P–N junction diode is :

(1) Concentration of positive and negative ions near the junction

(2) Concentration of positive charges near the junction

(3) Depletion of negative charges near the junction

(4) Increment in concentration of holes and electrons near the junction

Q.47 Common emitter circuit is used as amplifier, its current gain is 50. If input resistance is 1 kΩ and input voltage is 5 volt then output current will be :

(1) 250 mA (2) 30 mA

(3) 50 mA (4) 100 mA

Q.48 We consider a thermodynamic system. If ΔU represents the increase in its internal energy and W the work done by the system, which of the following statements is true ?

(1) ΔU = –W in an isothermal process

(2) ΔU = W in an isothermal process

(3) ΔU = –W in an adiabatic process

(4) ΔU = W in an adiabatic process

Q.49 A point Q lies on the perpendicular bisector of an electrical dipole of dipole moment p. If the distance of Q from the dipole is r (much larger than the size of the dipole), then the electric field at Q is proportional to :

(1) p² and r ^–3 (2) p and r^–2

(3) p^–1 and r^–2 (4) p and r^–3

Q.50 A particle, with restoring force proportional to displacement and resisting force proportional to velocity is subjected to a force F sin ωt. If the amplitude of the particle is maximum for ω = ω₁and the energy of the particle maximum for ω = ω₂, then :

(1) ω₁ ≠ ω₀ and ω₂ = ω₀

(2) ω₁ = ω₀ and ω₂ = ω₀

(3) ω₁ = ω₀ and ω₂ ≠ ω₀

(4) ω₁ ≠ ω₀ and ω₂ ≠ ω₀

Physics MCQ’s

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