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If the angular speed of rotation of an armature of alternating current generator is doubled, the induced e.m.f. will be
If 20 gm of a radioactive substance due to radioactive decay reduces to 10 gm in 4 minutes, then in what time 80 gm of the same substance will reduce to 10 gm
A radioactive nucleus undergoes αemission to form a stable element. What will be the recoil velocity of the daughter nucleus if V is the velocity of αemission and A is the atomic mass of radioactive nucleus
Three copper wires have lengths and crosssectional areas of (l and A), (2l and A/2) and (l/2 and 2A). Resistance will be minimum in
When a resistance of 2 Ω is connected across the terminals of a cell, the current is 0.5 amperes. When the resistance is increased to 5 ohm, the current is 0.25 amperes. The internal resistance of the cell is
An electron of charge 'E' is liberated from a hot filament and attracted by an anode of potential 'V' volts positive with respect to the filament. The speed of the electron of mass m when it strikes the anode is
The de Broglie wavelength λ associated with an electron having kinetic energy E is given by the expression
In a car spark coil, an e.m.f. of 40000 V is induced in a secondary when the primary current changes from 4 A to zero in 10μs. Find the mutual inductance between the primary and secondary windings of the spark coil
A parallel plate capacitor is first charged and then a dielectric slab is introduced between the plates. The quantity that remains unchanged is
An electric dipole placed in a nonuniform electric field experiences
A 60 kg weight is dragged on a horizontal surface by a rope to 2 metres. If coefficient of friction is μ=0.5, the angle of rope with the surface is 60^{o} and g=9.8 m/sec^{2}, then work done is
If distance between earth and sun become four times, then time period becomes
According to Kepler's third law (law of periods), the square of the time period of revolution of a planet around the sun is directly proportional to the cube of semimajor axis of its elliptical orbit,
ie, T^{2} ∝ R^{3}
where T is time taken by the planet to go one around the sun and R is semimajor axis (distance) of the elliptical orbit.
∴ T^{2} = kR^{3} .....(i)
where k is constant of proportionality.
When, R becomes 4 times let time period be T'
So, time period becomes 8 times of previous value.
In which of the following process, convection does not take place primarily?
The equation of state for 5 g of oxygen at a pressure P and temperature T, when occupying a volume V, will be (where R is the constant)
A potential difference of 2V exists across a potentiometer wire of 2m length. When the potential difference across a 2Ω resistance of a second circuit is measured by this potentiometer wire, it amounts to 5mm balancing length. The current in the second circuit is
2.5 mA
Potential gradient in the wire
The effective length of a magnet is 31.4 cm, and its pole strength is 0.5 Am. If it is bent in the form of a semicircle,then its new magnetic moment will be
When the free surface area of a liquid is increased, the surface tension of the liquid
If an airbubble of radius 0.4 mm at a depth h in water having surface tension of 72*10^{⁻3} Nm^{⁻1} and density 1000 kgm^{⁻3} is in equilibrium then, the value of h is (Take g=10 ms^{⁻2})
For a constant hydraulic stress on an object, the fractional change in the object's volume (Δ V/V) and its bulk modulus (K) are related as
A car is driven for 0.8 s. If the car travelling initially with 36 km − h^{⁻1} is stopped by the driver after observing a signal by deceleration of 5 m − s^{−2}, then total distance travelled by the car before coming to rest, is
A cricketer hits a ball with a velocity 25 m/s at 60^{o} above the horizontal. How far above the ground it passes over a fielder 50 m from the bat (assume the ball is struck very close to the ground)
The maximum speed of a car on a roadturn of radius 30 m, if the coefficient of friction between the tyres and the road is 0.4, will be
A person of 70kg mass is lifted by a helicopter with the help of rope hanging from it. If the helicopter is rising with an acceleration of 4 ms^{2}, the tension in the rope is (g=10 ms^{2})
The ability of eye to focus near as well as distant objects is called
When the potential energy of a particle executing simple harmonic motion is onefourth of the maximum value during the oscillation, its displacement from the equilibrium position in terms of its amplitude a is
Which of the following function represents a simple harmonic motion?
A ray of light is incident at 60^{o} on a prism of refracting angle 30^{o} . The emergent ray is at an angle 30^{o} with the incident ray. The value of refractive index of the prism is
Angle of prism = 30^{o} = A
Angle of incidence = i_{1} = 60^{o}
Angle of emergence = i_{2} = ?
Angle of devation = D = 30^{o}
∴ i_{2} = A + D  i_{2} = 30 + 30  60 = 0^{o}
⇒ r_{2} = 0^{o}
A person standing on a rotating platform has his hands lowered. He suddenly outstreches his arms. His angular momentum
A wheel is rotating at 900 r.p.m. about its axis When power is cut off it comes to rest in 1 minute The angular retardation in rad/s^{2} is
Two rings of the same radius and mass are placed such that their centres are at a common point and their planes are perpendicular to each other. The moment of inertia of the system about an axis passing through the centre and perpendicular to the plane of one of the ring is (mass = and radius = r)
The relation between Faraday constant (F), chemical equivalent (E) and electrochemical equivalent (Z) is
The densities of two substances are in the ratio 5:6 and their specific heats are in the ratio 3:5 respectively. Then their thermal capacities per unit volume will be in the ratio
At N.T.P. one mole of diatomic gas is compressed adiabatically to half of its volume (γ = 1.41). The work done on gas will be
For diffraction of light, the condition for nth secondary minimum is that path difference is equal to [Here a is the width of slit, n is the order of diffraction, λ is the wavelength of light and θ n gives the direction of nth secondary minimum ]
The displacement of the interfering light waves are y₁ = 4 sin ωt and y₂ = 3 sin (ωt + π/2). What is the amplitude of the resultant wave
Two waves of intensities I and 4 I superimpose, then maximum and minimum intensities are
A quarter horse power motor runs at a speed of 600 r.p.m. Assuming 40% efficiency the work done by the motor in one rotation will be
The average resisting force that must act on a 5 Kg mass to reduce its speed from 65cms^{1} to 15cms^{1} in 0.2s is
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