List of practice Questions

A potentiometer is used to measure the potential difference between A and B, the null point is obtained at 0.9 m. Now potential difference between A and C is measured, the null point is obtained at 0.3 m. The ratio \( \frac{E_2}{E_1} \) is \( (E_1>E_2) \)
Photodiode is a device
Two cars of masses \( m_1 \) and \( m_2 \) are moving in circles of radii \( r_1 \) and \( r_2 \) respectively. Their speeds are such that they make complete circles in the same time \( t \). The ratio of their centripetal force is
A circular current-carrying coil has radius \( R \). At what distance from the centre of the coil on the axis, the magnetic induction will become \( \frac{1}{\sqrt{8}} \) of its value at the centre of the coil?
In the case of conical pendulum, if \( T \) is the tension in the string and \( \theta \) is the semi-vertical angle of the cone, then the component of tension which balances the centrifugal force in equilibrium position is
A molecule consists of two atoms each of mass \( m \) and separated by a distance \( d \). At room temperature the average rotational kinetic energy is \( E \), then its angular frequency is
A cylindrical magnetic rod has length 5 cm and diameter 1 cm. It has uniform magnetization \( 5 \times 10^3 \, \text{A/m} \). Its net magnetic dipole moment is nearly
A uniform rod AB of mass \( m \) and length \( l \) is at rest on a smooth horizontal surface. An impulse \( P \) is applied to the end B. The time taken by the rod to turn through a right angle is
The magnitude of total energy and angular momentum of an electron in the \( n \)th orbit of a Bohr atom is denoted by \( E_n \) and \( L_n \), respectively. Then
A ray of light passes through an equilateral prism such that the angle of incidence is equal to angle of emergence and each of these angles is equal to \( \frac{1}{3} \)rd the angle of prism. The angle of deviation is
A pipe closed at one end has length 0.8 m. At its open end, a 0.5 m long uniform string is vibrating in its second harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is 50 N and the speed of sound is 320 m/s, the mass of the string is
Two identical parallel plate air capacitors are connected in series to a battery of e.m.f. \( V \). If one of the capacitors is inserted in liquid of dielectric constant \( K \), then potential difference of the other capacitor will become
From a disc of mass \( M \) and radius \( R \), a circular hole of diameter \( R \) is cut whose rim passes through the centre. The moment of inertia of the remaining part of the disc about perpendicular axis passing through the centre is
A glass convex lens is of refractive index 1.55 with both faces of same radius of curvature. What will be the radius of curvature if focal length is to be 20 cm?
In communication system, the range for line of sight propagation in case of earth is \( d \), for the height of antenna \( h \). If \( h \) is doubled then the new range is
A uniform metal wire of length \( L \), mass \( M \) and density \( \rho \) is under a tension \( T \). If the speed of transverse wave along the wire is \( V \), then area of cross-section of the wire is
The polarising angle for a transparent medium is \( \theta \) and \( v \) is the speed of light in that medium, then relation between \( \theta \) and \( v \) is (c = velocity of light)
In energy band diagram of insulators, a band gap and the conduction band is respectively
An alternating e.m.f. is given by \( e = e_0 \sin \omega t \). In what time the e.m.f. will have half its maximum value, if \( e_0 \) starts from zero? (T = Time period)
Due to surface tension, the excess pressure inside a smaller drop is 9 units. If 27 smaller drops combine, then the excess pressure inside the bigger drop is
The 3rd overtone of a closed organ pipe is in unison with 3rd overtone of an open pipe. The ratio of the length of the closed pipe to the length of open pipe is
What should be the velocity of earth due to rotation about its own axis so that the weight at equator becomes \( \frac{1}{25} \) of initial value?
(Radius of Earth on equator = 6400 km, \( g = 10 \, \text{m/s}^2 \), \( \cos 0^\circ = 1 \))
When a photosensitive surface is irradiated by lights of wavelengths \( \lambda_1 \) and \( \lambda_2 \), kinetic energies of emitted photoelectrons are \( E_1 \) and \( E_2 \) respectively. The work function of the photosensitive surface is
The unknown resistances are connected in two gaps of a metre bridge. The null point is at 20 cm from zero end. A resistance of 15 \( \Omega \) is connected in series with the smaller of the two. The null point shifts to 40 cm. The smaller resistance is
If a gas is compressed isothermally then the r.m.s. velocity of the molecules