A conducting sphere of radius 10 cm is charged with 10 μC. Another uncharged sphere of radius 20 cm is allowed to touch it for some time. After that if the spheres are separated, then surface density of charges on the spheres will be in the ratio
A capacitor of capacitance 2 μF is connected in the tank circuit of an oscillator oscillating with a frequency of 1 kHz. If the current flowing in the circuit is 2 mA, the voltage across the capacitor will be
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Two infinitely long parallel conducing plates having surface charge densities +σ and –σ are separated by a small distance. The medium between the plates is vacuum. If Ɛ0 is the dielectric permittivity of vacuum, then the electric field in the region between the plates is
The magnetic moment of current (I) carrying circular coil of radius (r) and number of turns (n) varies as:
An electric current passes through a long straight wire. At a distance 5 cm from the wire, the magnetic field is B. The field at a distance 20 cm from the wire would be
In a detector, output circuit consists of R = 10kΩ and C = 100 pF. The frequency of carrier signal it can detect is
Four resistances 10Ω, 5Ω, 7Ω and 3Ω are connected, so that they form the sides of a rectangle AB, BC, CD and DA, respectively. Another resistance of 10Ω is connected across the diagonal AC. The equivalent resistance between A and B is
In an experiment of finding the focal length of a concave mirror, a graph is drawn between the magnitudes of u and v. The graph looks like:
A photon of energy 4 eV is incident on a metal surface whose work function is 2 eV. The minimum reverse potential to be applied for stopping the emission of electrons is
The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately
Which of the following pairs does not have similar dimensions?
A body is released from the top of the tower H metre high. It takes t seconds to reach the ground. Where is the body after t/2 seconds of release?
A bomb of mass 3.0 kg explodes in air into two pieces of masses 2.0 kg and 1.0 kg. The smaller mass goes at a speed of 80 m/s. The total energy imparted to the two fragments is
A solid sphere of radius R is uniformly charged with charge density p in its volume. A spherical ft cavity of radius R/2 is made in the sphere as shown. Then electric potential at the centre of sphere will be
Three short dipoles each of dipole moment of magnitude p are placed on a circle of radius R as shown. The magnitude of electric field intensity at centre will be
Equipotential surfaces corresponding to electric field due to infinite charged sheet are
A galvanometer has a resistance 100 Ω. It gives full scale deflection on passing 10 mA current through it. To convert it into a voltmeter of range 0 - 10 V, the resistance to be added in series is
A charged particle q is shot from a large distance with speed v towards a fixed charged particle Q. It approaches Q upto a closest distance r and then returns. If velocity of q is halved, then the closest distance of approach would be
A particle having charge -q and mass m is released from rest on the axis of a fixed ring of total charge Q and radius R from a distance √3 R. Its kinetic energy when it reaches the centre of ring is
In the network shown points A, B and C have potential of 70 V, zero and 10V respectively.
The ratio of current in the section AD, DB and DC are
In a region of space, suppose there exists a electric field . The potential difference VA - Vo is (where VQ is the potential at the origin and VA the potential at x = 2 m is
In the experiment of the meter bridge if length corresponding to null deflection is x, what would be its value if the radius of meter bridge wire is doubled?
In the potentiometer circuit shown in figure, the internal resistance of the 12 V battery is 1Ω and length of the wire AB is 100 cm. When CB is 60 cm, the galvanometer show no deflection. The emf of cell E is (the resistance of wire AB is 3 Ω)
A cell of emf E and internal resistance r is connected in series with an external resistance nr. The ratio of the terminal potential difference to emf is
A total charge of 20 μC is divided into two parts placed at some distance apart. If the charges experience maximum coulombian repulsion, then the charges should be