List of top Physics Questions

A parallel plate capacitor with plate area \(A\) and plate separation \(d = 2\) m has a capacitance of \(4\mu F\). The new capacitance of the system if half of the space between them is filled with a dielectric material of dielectric constant \(K = 3\) (as shown in the figure) will be: 
 


 

In the following circuit diagram, when the \(3\Omega\) resistor is removed, the equivalent resistance of the network: 
 

A wire of resistance \(160\Omega\) is melted and drawn into a wire of one-fourth of its length. The new resistance of the wire will be:
Five cells each of emf \(E\) and internal resistance \(r\) send the same amount of current through an external resistance \(R\) whether the cells are connected in parallel or in series. Then the ratio \(\frac{R}{r}\) is:

The straight wire AB carries a current \(I\). The ends of the wire subtend angles \(\theta_1\) and \(\theta_2\) at the point \(P\) as shown in the figure. The magnetic field at the point \(P\) is: 
 


 

A long straight wire of radius \( a \) carries a steady current \( I \). The current is uniformly distributed across its cross-section. The ratio of the magnetic field at \( a/2 \) and \( 2a \) from the axis of the wire is:
The electrostatic force \( \mathbf{F_1} \) and magnetic force \( \mathbf{F_2} \) acting on a charge \( q \) moving with velocity \( v \) can be written as:
There are two long co-axial solenoids of the same length \( l \). The inner and outer coils have radii \( r_1 \) and \( r_2 \) and the number of turns per unit length \( n_1 \) and \( n_2 \), respectively. The ratio of mutual inductance to the self-inductance of the inner coil is:
A rectangular loop of length \( 2.5 \) m and width \( 2 \) m is placed at \( 60^\circ \) to a magnetic field of \( 4 \) T. The loop is removed from the field in \( 10 \) sec. The average emf induced in the loop during this time is:

Find the average value of the current shown graphically from \( t = 0 \) to \( t = 2 \) s. 
 

In an AC circuit, an inductor, a capacitor, and a resistor are connected in series with \( X_L = R = X_C \). The impedance of this circuit is:
An alternating voltage \( V(t) = 220 \sin 100\pi t \) volt is applied to a purely resistive load of \( 50\Omega \). The time taken for the current to rise from half of the peak value to the peak value is:
A parallel plate capacitor consists of two circular plates of radius \( R = 0.1 \) m. They are separated by a short distance. If the electric field between the capacitor plates changes as: \[ \frac{dE}{dt} = 6 \times 10^{13} \frac{V}{m \cdot s} \] then the value of the displacement current is:
Electromagnetic waves travel in a medium with speed \( 1.5 \times 10^8 \) m/s. The relative permeability of the medium is \( 2.0 \). The relative permittivity will be:
Power of a biconvex lens is \( P \) diopter. When it is cut into two symmetrical halves by a plane containing the principal axis, the ratio of the power of two halves is:
The magnifying power of a telescope is \( 9 \). When adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The ratio of the focal length of the objective lens to the focal length of the eyepiece is:
In a given semiconductor, the ratio of the number density of electron to number density of hole is 2 : 1. If $ \frac{1}{7} $th of the total current is due to the hole and the remaining is due to the electrons, the ratio of the drift velocity of holes to the drift velocity of electrons is :
A transformer which steps down 330 V to 33 V is to operate a device having impedance 110 $\Omega$. The current drawn by the primary coil of the transformer is:
A spring of spring constant \( 200 \, {N/m} \) is initially stretched by \( 10 \) cm from the unstretched position. The work to be done to stretch the spring further by another \( 10 \) cm is:
The capacitance of an isolated sphere of radius \( r_1 \) is increased by 5 times when enclosed by an earthed concentric sphere of radius \( r_2 \). The ratio \( \frac{r_1}{r_2} \) is:
A car travelling at 80 kmph can be stopped at a distance of 60 m by applying brakes. If the same car travels at 160 kmph and the same braking force is applied, the stopping distance is:
In a spring-block system as shown in the figure, if the spring constant \( K = 9 \, {N/m} \), then the time period of oscillation is:
A balloon carrying some sand of mass \( M \) is moving down with a constant acceleration \( a_0 \). The mass \( m \) of sand to be removed so that the balloon moves up with double the acceleration \( a_0 \) is:
What will be the acceleration due to gravity at a depth \( d \), where \( g \) is the acceleration due to gravity on the surface of the Earth?
The masses of a solid cylinder and a hollow cylinder are 3.2 kg and 1.6 kg respectively. Both the solid cylinder and hollow cylinder start from rest from the top of an inclined plane and roll down without slipping. If both the cylinders have equal radius and the acceleration of the solid cylinder is \( 4 { ms}^{-2} \), the acceleration of the hollow cylinder is: