The ratio of secondary to the primary turns in a transformer is 3:2. If the power output be P, then the input power neglecting all loses must be equal to
The rate of disintegration of fixed quantity of a radioactive element can be increased by
In an A.C. circuit, the current is i = 5 sin (100t-π/2) amp and the a.c. potential is V = 200 sin (100t) volt. Then, the power consumption is
Which one is not the correct statement?
An oxide coated filament is useful in vacuum tubes because essentially
The coefficient of linear expansion of brass and steel are α₁ and α₂. If we take a brass rod of length l₁ and steel rod of length l₂ at 0°C, their difference in length (l₂-l₁) will remain the same at a temperature if
Consider the following statements regarding the magnitude of barrier potential of a PN junction:
1. It is independent of temperature
2. It depends on difference between fermi levels on two sides of junction.
3. It depends on forbidden energy gap on two types of semiconductors
4. It depends on impurity concentration in P and N type semiconductors
Which of the statements given above is/are correct?
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
A shell is fired from a canon with velocity v m/sec at an angle θ with the horizontal direction. At the highest point in its path it explodes into two pieces of equal mass. One of the pieces retraces its path to the cannon and the speed in m/sec of the other piece immediately after the explosion is
Let '2m' be the mass of the cannon which is projected with velocity 'v' at an angle 'θ' with the horizontal direction
The horizontal component of the velocity of the cannon is, vx = v cosθ.
This component remains constant
At the maximum height, the cannon has only this component as the vertical component is momentarily zero
So, momentum before exploding = 2mv cosθ
After exploding one of the masses retraces the path of the cannon backwards
This is possible on if the part has velocity '-v cosθ'
Therefore, momentum after explosion = -mv cosθ + mu
So, by conservation of momentum
2mv cosθ = -mv cosθ + mu
⇒ u = (3v cosθ) m/s
A body of mass 5kg rests on a rough horizontal surface of coefficient of friction 0.2. The body is pulled through a distance of 10m by a horizontal force 25N. The kinetic energy acquired by it is (g = 10 ms−2)
The figure shows a charge q placed inside a cavity in an uncharged conductor. Now if an external electric field is switched on:
If the earth rotates faster than its present speed, then weight of an object will
The temperature of a body falls from 50°C to 40°C in 10 minutes. If the temperature of the surroundings is 20°C Then temperature of the body after another 10 minutes will be
The translational kinetic energy of gas molecule for one mole of the gas is equal to
A satellite in a force-free space sweeps stationary interplanetary dust at a rate (dM/dt) = αν. The acceleration of satellite is
The electric current in a circular coil of two turns produced a magnetic induction of 0.2T at its centre. The coil is unwound and is rewound into a circular coil of four turns. The magnetic induction at the centre of the coil now is, in tesla (if same current flows in the coil)
A vibration magnetometer is placed at South pole, then the time period will be
Hydraulic press is based on
When forces F1, F2, F3 are acting on a particle of mass m such that F2 and F3 are mutually perpendicular, then the particle remains stationary. If the force F1 is now removed, then the acceleration of the particle is
The particle remains stationary on the application of three forces that means the resultant force is 0.
F1 = - (F2 + F3)
Since, if the force F1 is removed, the forces acting are F2 and F3, the resultant of which has the magnitude of F1.
Therefore, the acceleration of the particle is F1 /m
A particle experiences a constant acceleration for 20 sec after starting from rest. If it travels a distance S₁ in the first 10 sec and a distance S₂ in the next 10 sec, then
A second's pendulum is mounted in a rocket. Its period of oscillation decreases when the rocket
A particle is viberating in a simple harmonic motion with an amplitude of 4 cm. At what displacement from the equilibrium position, is its energy half potential and kinetic ?
A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is
A hole in the bottom of the tank having water. If total pressure at bottom is 3 atm, then velocity of water flowing from hole is
A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. It the power of the original lens is 4D, the power of a cut lens will be
A particle performing uniform circular motion has angular momentum L. If its angular frequency is doubled, and its K.E. halved, then the new angular momentum is
In an experiment of simple pendulum, the errors in the measurement of length of the pendulum (L) and time period (T) are 3%v and 2% respectively. The maximum percentage error in the values of (L/T2) is
A mercury drop of radius 1cm is sprayed into 106 drops of equal size. The energy expended in joules is (surface tension of mercury is 460 x 10 − 3 Nm − 1)
A current i passes through a wire of length l, radius of cross-section r and density ρ. The rate of heat generation is
For a perfect gas, if α and β are volume and pressure coefficients of expansion.
Two samples, A and B, of a gas at the same initial temperature and pressure are compressed from volume V to V/2; A isothermally and B adiabatically. The final pressure of A will be
Which physical quantities have some dimensions?
In Young's double slit experiment, an interference pattern is obtained on a screen by a light of wavelength 6000 Å coming from the coherent sources S1 and S2. At certain point P on the screen third dark fringe is formed. Then the path difference S1p − S2p in microns is
Angle between wave velocity and particle velocity of a longitudinal wave is
A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is