If two charges \(q _1\) and \(q _2\) are separated with distance ' \(d\) ' and placed in a medium of dielectric constant \(K\). What will be the equivalent distance between charges in air for the same electrostatic force?

A radioactive sample has an average life of \(30\, {ms}\) and is decaying. A capacitor of capacitance \(200\, \mu\, {F}\) is first charged and later connected with resistor \(^{\prime}{R}^{\prime}\). If the ratio of charge on capacitor to the activity of radioactive sample is fixed with respect to time then the value of \(^{\prime}R^{\prime}\) should be \(....\,\Omega\)

A metal block of base area \(0.20\,m ^2\) is placed on a table, as shown in figure. A liquid film of thickness \(0.25\,mm\) is inserted between the block and the table. The block is pushed by a horizontal force of \(0.1\,N\) and moves with a constant speed. If the viscosity of the liquid is \(5.0 \times 10^{-3} \;Pa-s\), the speed of block is \(.........\times 10^{-3}\,m / s\)

Two stars of masses \(m\) and \(2\, m\) at a distance \(d\) rotate about their common centre of mass in free space. The period of revolution is

A shunt of resistance \(1\,\Omega \) is connected across a galvanometer of \(120\,\Omega \) resistance. A current of \(5.5\, ampere\) gives full scale deflection in the galvanometer. The current that will give full scale deflection in the absence of the shunt is nearly ............... \(ampere\)

Dimensions of universal gravitational constant \((G)\) in terms of Planck's constant \((h)\), distance \((L)\), mass \((M)\) and time \((T)\) are _______.

Match List - I with List - II.

List - I	List - II
(A) Permeability of free space	(I) \(\left[\mathrm{M} \mathrm{~L}^2 \mathrm{~T}^{-2}\right]\)
(B) Magnetic field	(II) \(\left[\mathrm{M} \mathrm{~T}^{-2} \mathrm{~A}^{-1}\right]\)
(C) Magnetic moment	(III) \(\left[\mathrm{M} \mathrm{~L} \mathrm{~T}^{-2} \mathrm{~A}^{-2}\right]\)
(D) Torsional constant	(IV) \(\left[\mathrm{L}^2 \mathrm{~A}\right]\)

Choose\(\text{ }\)the\(\text{ }\)correct\(\text{ }\)answer\(\text{ }\)from\(\text{ }\)the\(\text{ }\)options\(\text{ }\)given\(\text{ }\)below\(\text{ }\):

A load of mass \(M\,kg\) is suspended from a steel wire of length \(2\,m\) and radius \(1.0\,mm\) in Searle’s apparatus experiment. The increase in length produced in the wire is \(4.0\,mm.\) Now the load is fully immersed in a liquid of relative density \(2\). The relative density of the material of load is \(8\). The new value of increase in length of the steel wire is ........ \(mm\)

Two identical conducting spheres with negligible volume have \(2.1\, nC\) and \(-0.1\, nC\) charges, respectively. They are brought into contact and then separated by a distance of \(0.5 \,m\). The electrostatic force acting between the spheres is \(.......... \, \times 10^{-9} \,N\) [Given : \(4 \pi \varepsilon_{0}=\frac{1}{9 \times 10^{9}} SI\) unit]