WBJEE Physics Test - 7 - JEE MCQ

A parallel plate condenser with oil between the plates (dielectric constant of oil K = 2) has a capacitance C. If the oil is removed, then capacitance of the capacitors becomes

The quantity of electricity needed to liberate one gram equivalent of an element is

Consider telecommunication through optical fibres. Which of the following statements is not correct

A microammeter has a resistance of 100 Ω and full scale range of 50 μA. It can be used as a voltmeter or as a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination

The temperature coefficient of resistivity of material is 0.0004/K. When the temperature of the material is increased by 50ºC , its resistivity increases by 2 x 10^-8   o h m -meter. The initial resistivity of the material in ohm-meter is

A wire of length L is drawn such that its diameter is reduced to half of its original diameter. If the initial resistance of the wire were 10 Ω, its new resistance would be

The expected energy of the electrons at the absolute zero is called

If the length of the wire is doubled and its area of cross section is decreased to half, then its resistance

A transformer is used to light a 100W and 110V lamp from a 220V mains. If the main current is 0.5A, the efficiency of the transformer is approximately

The effective value of a.c. in a circuit is 10 A. The peak value of current is

In a current carrying long solenoid, the field produced does not depend upon

Which of the following radiations have the least wavelength?

If the electric flux entering and leaving an enclosed surface respectively is φ 1 and φ 2 , the electric charge inside the surface will be

Two charges -10 C and + 10 C are placed 10cm apart. Potential at the centre of the line joining two charges is

A parallel plate capacitor is first charged and then a dielectric slab is introduced between the plates. The quantity that remains unchanged is

Equal charges are given to two conducting spheres of different radii. The potential will

A charged particle begins to move from the origin in a region which has a uniform magnetic field in the x-direction and a uniform electric field in the y-direction. Its speed is ν, when it reaches the point (x,y,z). The speed (ν) will depend upon

The capacitor of a parallel plate capacitor with no dielectric substance and a separation of 0.4 cm is 2 μF. The separation is reduced to half and it is filled with a substance of dielectric value 2.8. The new capacity of the capacitor is

The path of particle moving under the influence of a force fixed in magnitude and direction is

In radioactive decay process, the negatively charged emitted β -particles are

What is the Q-value of the reaction

The atomic masses of ¹H , ⁴H e and ⁷L i are 1.007825 u, 4.002603 u and 7.016004 u respectively

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

What is the stopping potential when the metal with work function 0.6 eV is illuminated with the light of 2 eV ?

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

Time of exposure for a photographic print is 10 second, when a lamp of 50 Cd is placed at 1 m from it. Then another lamp of luminous intensity I is used, and is kept at 2 m from it. If the time of exposure now is 20 s, the value of I in (in Cd) is :

Two plane mirrors inclined to each other at an angle 72º , what is the number of images formed?

The minimum potential difference between the base and emitter required to switch a silicon transistor 'ON' is approximately