The primary of a step-down transformer used for ringing door bell has 2000 turns of fine wire and the secondary has 100 turns. This transformer, when connected to a 110 V a.c. source, will deliver at its secondary a potential difference of
A charge is moving in a uniform magnetic field in a circular path of radius R. If the energy of the particle is doubled, the new radius is
1 Crore+ students have signed up on EduRev. Have you? Download the App |
Increasing the charge on the plates of a capacitor means
When a resistance of 2 ohm is connected across the terminals of a cell, the current is 0.5 A. When the resistance is increased to 5 ohm, the current is 0.25 A. The e.m.f. of the cell is
The inductance of a coil is L = 10 H and resistance R = 5 Ω . If applied voltage of battery is 10 V and it switches off in 1 millisecond, find induced emf of inductor.
When a 12 Ω resistor is connected with a moving coil galvanometer then its deflection reduces from 50 divisions to 10 divisions. The resistance of the galvanometer is
Racitor eactance of a capof capacitance CμF for a.c. of frequency 400/π Hz is 25 Ω. The value of C is
A particle is moving on the inside of a smooth sphere of radius a, describes a horizontal circle at a distance a 2 below the centre of the sphere. Its speed is then-
Which of the following electromagnetic waves have the smallest wavelength?
Two electric charge 12 μC and −6 μC are places 20 cm apart in air. There will be a point P at which electric potential is zero on the line joining these two charges and outside, excluding the region between them. The distance of P from −6 μC charge is
A conducting sphere of radius 10 cm is charged with 10 μC. Another uncharged sphere of radius 20 cm in allowed to touch it for some time. If both the spheres are separated, then surface density of charges on the spheres will be in the ratio of
A block of mass 10kg is pushed by a force F on a horizontal rough plane moves with an acceleration 5 ms-2 When force is doubled, its aceleration becomes 18 ms-2 . The coefficient of friction is (g = 10 ms-2 ).
If acceleration due to gravity on the earth's surface is g, then value of acceleration due to gravity at a height of 32 km above the earth's surface is
A body of mass m is taken to the bottom of a deep mine. Then
A monochromatic beam of light is used for the formation of fringes on the screen by illuminating two slits in the Young's double-slit interference experiment. When a thin film of mica is interposed in the path of one of the interfering beams, then
The root mean square speed of hydrogen molecules at 300 K is 1930 m/s. Then the root mean square speed of oxygen molecules at 900 K will be
The temperature of a body falls from 50oC to 40oC in 10 minutes. If the temperature of the surroundings is 20oC Then temperature of the body after another 10 minutes will be
The magnetic induction at the centre of a current carrying circular coil of radius 10cm is 5√5 times the magnetic induction at a point on its axis. The distance of the point from the centre of the coil in cm is
An electron (charge q coulomb) enters a magnetic field of H weber/m2 with a velocity of ν m/s in the direction as that of the field. The force on the electron is
There are three voltmeters of the same range but of resistance 10000 Ω, 8000 Ω and 4000 Ω respectively. The best voltmeter among these is the one whose resistance is
The magnetic needle of a vibration magnetometer makes 12 oscillations per minute in the horizontal component of earth's magnetic field. When an external short bar magnet is placed at some distance along the axis of the needle in the same line, it makes 15 oscillations per minute. If the poles of the bar magnet are interchanged, the number of oscillations it makes per minute is
Isogonic lines on magnetic map represent the lines of
The couple acting on a magnet of length 10cm placed in a uniform magnetic field of intensity 40N/wb such that the axis of the magnet makes 45o with the field direction is 2 ∕ 10 Nm. The pole strength of the magnet in webers
Two mercury drops with radii in the ratio of 3 : 4 fall from a great height through the viscous liquid. The ratio of their terminal velocities is
In a liquid flowing through a pipe, the pressure difference between its ends is made half and radius is doubled. If the initial rate of flow of liquid was Q, then new rate of flow of liquid through the pipe is
A wire of length L and cross-section A is made of material of Young's modulus Y. If it is stretched by an amount x, then work done is
Two discs of same thickness but of different radii are made of two different materials such that their masses are same. The densities of the materials are in the ratio 1:3. The moments of inertia of these discs about the respective axes passing through their centres and perpendicular to their planes will be in the ratio
From the top of a tower, a particle is thrown vertically downwards with a velocity of 10 m/s. The ratio of the distances, covered by it in the 3rd and 2nd seconds of the motion is (Take g=10m/s2)
A body weighs 8 gm when placed in one pan and 18 gm when placed on the other pan of a false balance. If the beam is horizontal when both the pans are empty, the true weight of the body is
The material used to slow down neutrons in a reactor is called
4 videos|8 docs|51 tests
|
4 videos|8 docs|51 tests
|