WBJEE Physics Test - 8

Energy per unit volume for a capacitor having area A and separation d kept at potential difference V is given by

Same current is being passed through a copper voltmeter and a silver voltmeter. The rate of increase in weights of the cathode of the two voltmeters will be proportional to

If a wire of resistance R is melted and recasted to half of its length, then the new resistance of the wire will be

A laser beam is used for carrying out surgery because it

Given three equal resistors, how many different combination of all the three resistors can be made?

In the circuit,the galvanometer G shows zero deflection. If the batteries A and B have negligible internal resistance, the value of the resistor R will be

A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 kV, its kinetic energy will be

For a metallic wire, the ratio V/i (V= the applied potential difference, i= current flowing) is

Choke coil works on the principle of

In an L-R circuit, time constant is that time in which current grows from zero to the value

Lenz's law is a consequence of the law of conservation of

Which of the following radiations have the least wavelength?

A charge is placed at the centre of a cube, the flux emitted through its one face is

On moving a charge of 20 C by 2 cm, 2 joule of work is done, then the potential difference between the points is

Two equal charges q of opposite sign separated by a distance 2a constitute an electric dipole of dipole moment p. If P is a point at a distance r from the centre of the dipole and the line joining centre to this point makes an angle θ with the axis of the dipole, then potential at the point P is given by

The capacitance of a parallel plate capacitor becomes 4/3 times its original value if a dielectric slab of thickness t = d/2 is inserted between the plates (where d is separation between the plates). The dielectric constant of the slab is

Five equal capacitors connected in series have a resultant capacitance of 4 μ F. The total energy stored in these, when these are connected in parallel and charged to 400V is

Two point charges of +4 μC and -6 μC are separated by a distance of 20 cm in air. At what point, on the line joining the two charges from charge +4 μC, the electric potential will be zero?

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

In β ⁺ decay process, the following changes take place inside the nucleus

In a chain reaction uranium atom gets fissioned forming two different materials. Then total weight of these put together is

Sodium surface is subjected to ultraviolet and infrared radiations separately and the stopping potential of photoelectrons determined. Then the stopping potential is

An alpha nucleus of energy bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

An image of the sun is formed by a lens of focal length 30 cm on the metal surface of a photoelectric cell and a photoelectric current (I) is produced. The lens forming the image is then replaced by another of the same diameter but of focal length of 15 cm. The photelectric current in this case is

If the luminous intensity of a unidirectional bulb is 100 candela, then total luminous flux emitted from the blub, is

A concave lens of focal length 20 cm placed in contact with a plane mirror acts as a

In case of a semiconductor which one of the following statements is wrong?

Indium impurity in Germanium makes it into a

Fermi level in an intrinsic semiconductor lies

Platinum and silicon are heated upto 250ºC and after then cooled. In the process of cooling

Which of the following, when added as an impurity atom in the silicon, produces n-type semiconductor?

In a P-N junction diode

A semiconductor is cooled from T₁K to T₂K. Its resistance

Which one of the following properties of light does not support wave theory of light?

A Nicol prism can be used

Inverse square law of intensity (illuminance) is valid for

When exposed to sunlight, thin films of oil on water often exhibit brilliant colours due to the phenomenon of