A circuit has a resistance of 12 ohm and an impedance of 15 ohm. What will be the power factor of the circuit?
The self inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of
One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v, then the emf induced in the circuit in terms of B, l and v where l is the width of each tube, will be
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radian per second. If the horizontal component of earth’s magnetic field is 0.2 × 10-4 T, then the e.m.f. developed between the two ends of the conductor
In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to
In a uniform magnetic field of induction B a wire in the form of a semicircle of radius r rotates about the diameter of the circle with angular frequency 
. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R the mean power generated per period of rotation is
A coil having n turns and resistance R 
is connected with a galvanometer of resistance 4R . This combination is moved in time t seconds from a magnetic field W1 weber to W2 weber. The induced current in the circuit is
Alternating current cannot be measured by D.C. ammeter because
In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50 V. What will be the voltage across the LC combination?
The core of any transformer is laminated so as to
In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is
When the current changes from +2 A to –2 A in 0.05 second, an e.m.f. of 8 V is induced in a coil. What is the coefficient of selfinduction of the coil?
Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon
elative permittivity and permeability of a material are 
and 
, respectively. Which of the following values of these quantities are allowed for a diamagnetic mateiral?
Needles N1, N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will
A magnetic needle is kept in a nonuniform magnetic field. It experiences
The materials suitable for making electromagnets should have
The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. What will be the time period of this combination?
There are several types of enzyme catalysed reactions. In
one type of enzyme catalysed reaction, in addition to the
catalytic site to which the substrate (X) binds, the enzyme
also has a site to which some other substance (Y) can bind.
When Y binds to such an enzyme, the enzyme can still bind
to the substrate but cannot convert it to the product. Which
of the following will occur in such a case?
In an experiment, E. coli cells growing at 37°C were shifted to 20°C and grown for a few generations. Which of the
following changes in the membrane would help the E. coli cells adapt to the new environment?
A cladogram that classifies five species (M, N, O, P and Q) is shown below.Which of the six dots in the cladogram corresponds to the most recent common ancestor of N and P?
During the growth of marine fish, initially, yolk sac and skin are the principal sites where transport protein ‘x’ is located. Later, skin and gills become principal sites and finally ‘x’ becomes localised to gills. The protein ‘x’ is
A horizontal overhead powerline is at a height of 4 m from the ground and carries a current of 100 A from east to west. The magnetic field directly below it on the ground is
Two identical conducting wires AOB and COD are placed at right angles to each other. The wire AOB carries an electric current I1 and COD carries a current I2. The magnetic field on a point lying at a distance d from O, in a direction perpendicular to the plane of the wires AOB and COD, will be given by
A charged particle moves through a magnetic field perpendicular to its direction. Then
A charged particle with charge q enters a region of constant, uniform and mutually orthogonal fields 
and 
with a velocity 
perpendicular to both and , and comes out without any change in magnitude or direction of . Then
A current I flows along the length of an infinitely long, straight, thin walled pipe. Then
What is the inductance between A and D?
elative permittivity and permeability of a material are and , respectively. Which of the following values of these quantities are allowed for a diamagnetic mateiral?
Needles N1, N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will
A magnetic needle is kept in a nonuniform magnetic field. It experiences
In a transformer, number of turns in the primary coil are 140 and that in the secondary coil are 280. If current in primary coil is 4 A, then that in the secondary coil is
The power factor of an AC circuit having resistance (R) and inductance (L) connected in series and an angular velocity 
is
A long solenoid has 200 turns per cm and carries a current i. The magnetic field at its centre is 6.28 × 10-2 Wb/m2. Another long solenoid has 100 turns per cm and it carries a current i/3. What will be the value of the magnetic field at its centre?
In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. What will be the path of the particle?
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity then
A charged particle of mass m and charge q travels on a circular path of radius r that is perpendicular to a magnetic field B. What will be the time taken by the particle to complete one revolution?
Two concentric coils each of radius equal to 
cm are placed at right angles to each other. 3 ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in weber/m2 at the center of the coils will be 
A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be
Two thin long, parallel wires, separated by a distance d carry a current of i A in the same direction. They will
Two long conductors, separated by a distance d carry current I1 and I2 in the same direction. They exert a force F on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance is also increased to 3d. What will be the new value of the force between them?
The magnetic field due to a current carrying circular loop of radius 3 cm at a point on the axis at a distance of 4 cm from the centre is 54 
What will be its value at the centre of the loop?
A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is B. It is then bent into a circular loop of n turns. What will be the magnetic field at the centre of the coil?
A current i ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube is
An ammeter reads upto 1 ampere. Its internal resistance is 0.81 ohm. To increase the range to 10 A the value of the required shunt is
A particle of charge –16×10-18 coulomb moving with velocity 10 ms-1 along the x-axis enters a region where a magnetic field of induction B is along the y-axis, and an electric field of magnitude 104 V/m is along the negative z-axis. If the charged particle continues moving along the xaxis, then what will be the magnitude of B?
A particle of mass M and charge Q moving with velocity
describes a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. What will be the work done by the field when the particle completes one full circle?
The time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of its
If a current is passed through a spring then the spring will
If an electron and a proton having same momenta enter perpendicular to a magnetic field, then