In a transformer, current and e.m.f. in the output is 10 A and is 220 V respectively. If ratio of no. of turns in secondary and primary coil 50:10, then current in the primary coil is
The activity of a radiactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay cosntant is approximately
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A galvanometer coil has a resistance of 10 Ω and the meter shows full scale deflection for a current of 1mA. The shunt resistance required to convert the galvanometer into an ammeter of range 0-100mA is about
A body of mass m moving with a constant velocity ν hits another body of the same mass moving with the same velocity ν but in the opposite direction and sticks to it. The velocity of the compound body after collision is
When ultraviolet rays are incident on metal plate, then photoelectric effect does not occurs. It occurs by the incidence of
A small solid cylinder rolls up along a curved surface (fig.) with an initial velocity v. It will ascend up to a height ‘h’ equal to
If a positive charge is shifted from a low potential region to a high potential region, then the electric potential energy of the system
A block of mass 50 kg can slide on a rough horizontal surface. The coefficient of friction between the block and the surface is 0.6. The least force of pull acting at an angle of 30o to the upward drawn vertical which causes the block to just slide is
An oscillator circuit consists of an inductance of 0.5 mH and a capacitor of 20 μF. The resonance frequency of the circuit is
According to Kepler's law the time period of a satellite varies with its radius are as
Consider two rods of same length and different specific heatrs (s₁ and s₂) conductivities k₁ and k₂ and areas of cross section (A₁ and A₂) and both giving temperature T₁ and T₂ at their ends. If the rate of heat loss due to conduction is equal, then
R.M.S. velocity of a particle is V at pressure P. If pressure is increased two times, then the R.M.S. velocity becomes
A gun fires the bullets each of mass 10 g with a velocity of 50 m−s-1. If 1000 bullets are fired per second, then thrust on the shoulder will be
A length of wire carries a steady current. It is bent first to form a circular coil of one turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is
Rate of change of torque τ with deflection θ is maximum for a magnet suspended freely in a uniform magnetic field of induction B, when
Sixty four spherical rain drops of equal size are falling vertically through air with a terminal velocity 1.5 m-s-1. If these drops coalesce to form a big spherical drop, then terminal velocity of big drop is
A body at rest is dropped from a height h and strikes the ground with a velocity 3 m/s. Another body of same mass is dropped from the same height with an initial velocity of 4 m/s. The final velocity of second mass, with which it strikes the ground, is (take g=10 m/s2)
At the uppermost point of a projectile, angle between the directions of its velocity and acceleration is
If a bullet of mass 5 gm moving with velocity 100 m/sec, penetrates the wooden block upto 6 cm. Then the average force imposed by the bullet on the block is
The time period of a body executing simple harmonic motion is 4 s. After how much interval, from time t = 0, its displacement will be half of its amplitude?
10 cm long wire is placed horizontally on the surface of water and is gently pulled up with a forceof 2 x 10⁻-2N to keep the wire in equilibrium. The surface tension of water in N/m is
The horizontal range is four times the maximum height attained by a projectile. The angle of projection is
A solid cylinder of mass M and radius R rolls on a flat surface. Its moment of inertia about the line of contact is
The dimensions of resistance x capacitance are same as those of
The lower end of a capillary tube touches a liquid whose angle of contact is 90o . The liquid
A current i passes through a wire of length l, radius of cross-section r and density ρ. The rate of heat generation is
The apparent coefficient of expansion of a liquid, when heated in a copper vessel is 'C' and when heated in a silver vessel is 'S'. If 'A' is the linear coefficient of expansion of copper, then the linear, coefficient of expansion of silver is
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1 videos|1 docs|68 tests
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