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If the work function of a metal is 3.7 eV When a photon of energy 5.2 eV falls on the metal surface then the kinetic energy of ejected photoelectrons will be

Answer: 1.5 eV Solution: K.E = 5.2 - 3.7 = 1.5 eV... View Article

In the R−C circuit shown in the figure, the total energy of 3.6×10⁻³ J is dissipated in the 10 Ω resistor when the switch S is closed. The initial charge on the capacitor is:

a) 60 μC b) 120 μC c) 60√2 μC d) 60/√2 μC Answer: b) 120 μC Solution: When S is closed, the energy stored in the capacitor will be... View Article

A body released from the top of a tower falls through half the height of the tower in 3 s. It will reach the ground after nearly

b) 3.5 s c) 4.24 s d) 4.71 s d) 6 sec Answer: d) 4.24 s Solution: Let (h) be the total height of the tower Time taken by the body to... View Article

A cylindrical tub of radius 16 cm contains water to the depth of 30 cm. A spherical iron ball is dropped into the tub, as a result, the level of water rises by 9 cm. The radius of the ball is

a) 10 cm b) 6 cm c) 12 cm d) None of the above Answer: c) 12 cm Solution: Let r be the radius of the iron ball Then, Volume of... View Article

If earth suddenly stops rotating, then the weight of an object of mass m at equator will [ω is angular speed of earth and R is its radius ] :

a) decreases by mω2R b) increase by mω2R c) decrease by mmωR2 d) increase by mωR2 Answer: b)... View Article

An aeroplane of mass 3×10⁴ kg and a total wing area of 120 m² is in a level flight at the same height. The difference in pressure between the upper and lower surface of its wings in Kilo Pascal is( g = 10 ms⁻²)

a) 2.5 b) 5.0 c) 10 d) 12.5 Answer: a) 2.5 Solution: Pressure, Δp=F/A =mg/A =(3×104×10)/120 =2.5 x 103 = 2.5 kPa... View Article

The electric potential changes from 10 V to 30 V as one moves along x-axis from x = 0 to x = 2m . The magnitude of the electric field in the origin is

a) 10 V/m b) 20 V/m c) 5 V/m d) Both (a) and (b) Answer:a) 10 V/m Solution: E = (30 - 10)/(2-0)= 20/2 = 10 V/m... View Article

A battery of emf 2 V and internal resistance 0.5 Ω is connected across a resistance of 9.5 Ω. How many electrons cross through a cross-section of the resistance in 1 second?

Answer: 1.25 x 1018 Solution: Req = 0.5 + 9.5 = 10 Ω The current in the circuit is i = 2v/(10Ω) = 0.2 A Thus,... View Article

A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively. Then, this region of space may have

a) E = 0, B = 0 b) E = 0, B ≠ 0 c) E ≠ 0, B = 0 d) E ≠ 0, B ≠ 0 Answer: a, b, d Solution: a) If E... View Article

A rod AB slides on a V-shaped wire with speed v as shown, such that at any time OA=OB=l. The magnetic field in the region is perpendicular downwards and has strength B, the induced emf in the rod is

a) zero b) Bvl c) √3Bvl/2 d) Bvl/2 Answer: b) Bvl Solution: Given, OA=OB=l Since OA and OB are equal ∠OBA and ∠OAB are also equal ∠OBA... View Article

A block of mass m is placed at rest on an inclined plane of inclination θ to the horizontal. If the coefficient of friction between the block and the plane is μ, then the total force exerted by the inclined plane on the block is:

a) mg b) μmgcosθ c) mg sinθ d) μmgtanθ Answer: a) mg Solution: The total force exerted by block =mg,... View Article

A boy weighing 25 kg climbs up from the first floor at a height 3 m above the ground to the third floor at a height 9 m above the ground. What will be the increase in his gravitational potential energy? (Take g=10Nkg⁻¹)

a) 1500 J b) 0 J c) 150 J d) 2250 J Answer: a) 1500 J Solution: P.E=mgh In the first case that is in 3 m... View Article

28 Dec 2021: UPSC Exam Comprehensive News Analysis

CNA 28 Dec 2021:- Download PDF Here TABLE OF CONTENTS A. GS 1 Related B. GS 2 Related HEALTH 1. Kerala tops NITI Aayog Health Index; U.P. at... View Article

27 Dec 2021: PIB Summary & Analysis

TABLE OF CONTENTS 1. Network Readiness Index (NRI) 2021 2. 6G Technology Innovation Group 3. Air pollution 1. Network Readiness... View Article