A motor having an armature of resistance 2Ω is designed to operate at 220 V mains. At full speed, it develops a back e.m.f. of 210V. When the motor is running at full speed, the current in the armature is
An electron is travelling horizontally towards east. A magnetic field is vertically downward direction exerts a force on the electron in the direction of
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Three capacitors, each of capacity 4 μF are to be connected in such a way that the effective capacitance is 6 μF. This can be done by
A photon of energy 4 eV is incident on a metal surface whose work function is 2 eV. Minimum value of reverse potential to be applied for stopping the emission of electrons is
When subjected to a transverse electric field, cathode rays move
A body of mass m1 moving with a velocity 10ms-1 collides with another body at rest of mass m2. After collision the velocities of the two bodies are 2 ms-1 and 5 ms-1 respectively along the direction of motion of m1. The ratio m1/m2 is
A galvanometer of resistance 25 Ω gives full scale deflection for a current of 10 milliampere, is to be changed into a voltmeter of range 100 V by connecting a resistance of 'R' in series with galvanometer. The value of resistance R in Ω is
According to Einstein's photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal versus frequency of the incident radiation gives a straight line, whose slope
The ratio of specific charge of an α-particle to that of a proton is
A 220 V, 1000 watt bulb is connected across a 110 V mains supply. The power consumed will be
The current in a coil changes from 4 A to zero in 0.1 s. If average e.m.f. induced is 100 V, what is self-inductance of coil ?
What is the value of inductance L for which the current is a maximum in series LCR circuit with C = 10 μF and ω = 1000 s−1 ?
An electromagnetic wave passing through vacuum is described by the equations: E = E₀ sin (kx-ωt) and B = B₀ sin (Kx-ωt). Then
Six identical +ve charges, each +Q and two identical charges, each −Q are fixed at the corners of cube of edge a. The negative charges are located at diagonally opposite corners. The electo potential energy of the system is
If the K.E of a particle is doubled, then its momentum will
A particle of mass m has momentum p. its kinetic energy will be
The electric potential at any point (x,y,z) in a space is given by: V=4x2 volt. The electric field at (1,0,2) m in space is
The temperature of hot and cold end of a 20 cm long rod in thermal steady state are at 100ºC and 20ºC respectively. Temperature at the centre of the rod is
An electric kettle takes 4 A current at 220 V. How much time will it take to boil 1 kg of water from room temperature 20ºC? The temperature of boiling water is 100ºC.
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
A magnet freely suspended in a vibration magnetometer makes 40 oscillations per minute at a place 'A' and 20 oscillations per minute at a place 'B'. If the horizontal component of earth's magnetic field at 'A' is 36 x 10−6T, then its value at 'B' is
A metallic wire is suspended by attaching some weight to it. If α is the longitudinal strain and Y is Young's modulus, then the ratio between elastic potential energy and the energy density is equal to
Three light strings are connected at the point P. A weight W is suspended from one of the strings .End A of string AP and end B of string PB are fixed as shown .In equilibrium PB is horizontal and PA makes an angle of 60º with the horizontal .If the tension in PB is 30 N then the tension in PA and weight W are respectively
The half-life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is-
A particle of mass 0.1 kg is undergoing simple harmonic motion of amplitude 1m and period 0.2 second. If the oscillations are produced by a spring, what is the force consrant of the spring ?
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): In a system with damping effect, 100% of the total energy can be the maximum potential energy.
Reason(R): Minimum potential energy will be treated as zero point energy and will also be non-zero.
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Kirchhoff's first law expresses the law of conservation of energy .
Reason(R): When a steady current flows in a circuit there is neither any acumulation of charge at any point in the circuit nor any charge is removed from there .
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A):The quartz fibres in moving coil galvanometer are silvered .
Reason(R): Silvered surface reflects maximum light.
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Air quickly leaking out of a balloon becomes cooler.
Reason(R): The leaking air undergoes adiabatic expansion. Reason(R): The leaking air undergoes adiabatic expansion.