List of practice Questions

A zener diode of power rating 1.6 W is used as a voltage regula tor. If the zener diode has a breakdown voltage of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V, what is the value of resistance Rs for safe operation of the diode?

The angular momentum for the electron in Bohr’s orbit is L. If the electron is assumed to revolve in second orbit of hydrogen atom, then the change in angular momentum will be

The energy of an electromagnetic wave contained in a small volume oscillates with

Given below are two statement :  
Statement I : If the number of turns in the coil of a moving coil galvanometer is doubled then the current sensitivity becomes double.  
Statement II : Increasing current sensitivity of a moving coil galvanometer by only increasing the number of turns in the coil will also increase its voltage sensitivity in the same ratio.
In the light of the above statement, choose the correct answer from the options given below : 

Two wires each of radius 0.2 cm and negligible mass, one made of steel and other made of brass are loaded as shown in the figure. The elongation of the steel wire is _____ x 10-6 m .

[Young’s modulus for steel = 2 x 1011 Nm-2 and g = 10ms-2]

A transverse harmonic wave on a string is given by y(x,t) = 5 sin(6t + 0.003x) where x and y are in cm and t in sec. The wave velocity is _______ ms-1 

Let B and C be the two points on the line \(y + x = 0\) such that B and C are symmetric with respect to the origin. Suppose A is a point on \(y – 2x = 2\) such that \(\Delta ABC\) is an equilateral triangle. Then, the area of the \(\Delta ABC\) is

Unpolarised light of intensity 32Wm^-2 passes through the combination of three polaroids such that the pass axis of the last polaroid is perpendicular to that of the pass axis of first polaroid. If intensity of emerging light is 3Wm^-2 , then the angle between pass axis of first two polaroids is ______º .

Three concentric shells A, B and C having surface charge density σ, –σ and σ respectively. The radii of A and B are 2 cm and 3 cm respectively. Electric potential at surface A is V_A and at C is V_C. If V_A = V_C then find the radius of C in cm.

A solenoid having 60 turns and length 15 cm produces magnetic field of 2.4 × 10^–3 T, Find the current in the solenoid

10 resistors each of resistance 10Ω can be connected in such as to get maximum and minimum equivalent resistance. The ratio of maximum and minimum equivalent resistance will be_______ .

A car P travelling at 20 \(ms^{–1}\) sounds its horn at a frequency of 400 Hz. Another car Q is travelling being the first car in the same direction with a velocity 40 \(ms^{–1}\) . The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound = 360 \(ms^{–1}\) ]

A capacitor of capacitance C is charged to a potential V. The flux of the electric field through a closed surface enclosing the positive plate of the capacitor is :

A plane electromagnetic wave of frequency 20 MHz propagates in free space along x-direction. At a particular space and time, \(\overrightarrow E =6.6 \;\hat jV/m  .\)What is \(\overrightarrow B\) at this point ?

The energy of \(He^+\) ion in its first excited state is, (The ground state energy for the Hydrogen atom is – 13.6 eV) :

If force (F), velocity (V) and time (T) are considered as fundamental physical quantity, then dimensional formula of density will be :

An electron is allowed to move with constant velocity along the axis of current carrying straight solenoid.
A. The electron will experience magnetic force along the axis of the solenoid. 
B. The electron will not experience magnetic force. 
C. The electron will continue to move along the axis of the solenoid. 
D. The electron will be accelerated along the axis of the solenoid. 
E. The electron will follow parabolic path-inside the solenoid. 
Choose the correct answer from the options given below :

The root mean square speed of molecules of nitrogen gas at 27°C is approximately : (Given mass of a nitrogen molecule = \(4.6 × 10^{–26}\) kg and take Boltzmann constant KB = \(1.4 × 10^{–23}\) JK–1 )

The current flowing through \(R_2\) is

In satellite communication, the uplink frequency band used is :

A body of mass 500 g moves along x-axis such that it's velocity varies with displacements x according to the relation \(v  =10 \sqrt x\) m/s the force acting on the body is :

Eight equal drops of water are falling through air with a steady speed of 10 cm/s. If the drops coalesce, the new velocity is :

When one light ray is reflected from a plane mirror with 30° angle of reflection, the angle of deviation of the ray after reflection is :