List of top Physics Questions

A point charge \(+10 µC\) is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)
 

Two charges 2 μC and –2 μC are placed at points A and B 6 cm apart.

(a) Identify an equipotential surface of the system.

(b) What is the direction of the electric field at every point on this surface?

A 4.5cm needle is placed 12cm away from a convex mirror of focal length 15cm. Give the location of the image and the magnification.Describe what happens as the needle is moved farther from the mirror.

A regular hexagon of side 10 cm has a charge 5 μC at each of its vertices. Calculate the potential at the centre of the hexagon.
Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is \(8.0 × 10^3 N m^2 C^{-1}. \)
(a) What is the net charge inside the box? 
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or Why not?

A small candle,2.5cm in size is placed at 27cm in front of a concave mirror of radius of curvature 36cm.At what distance from the mirror should a screen be placed in order to obtain a sharp image? Describe the nature and size of the image.If the  is moved closer to the mirror, how would the screen have to be moved?

Consider a uniform electric field \(E = 3 × 10^3 \,\hat{i} NC^{-1}\). 
(a) What is the flux of this field through a square of 10 cm on a side whose plane is parallel to the yz - plane? 
(b) What is the flux through the same square if the normal to its plane makes a \( 60^0\) angle with the x-axis?
A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is \(1.5 × 10^3 NC^{-1}\) and points radially inward, what is the net charge on the sphere?
What is the net flux of the uniform electric field of Exercise 1.15 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes?
(a) Two insulated charged copper spheres A and B have their centers separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is \(6.5 × 10^{−7} C\)? The radii of A and B are negligible compared to the distance of separation. 
(b) What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?
A polythene piece rubbed with wool is found to have a negative charge of \(3 × 10^{−7} C\). 
(a) Estimate the number of electrons transferred (from which to which?) 
(b) Is there a transfer of mass from wool to polythene?
A charged particle oscillates about its mean equilibrium position with a frequency of $10^9\, Hz$. The frequency of electromagnetic waves produced by the oscillator is
A radio can tune to any station in $7.5\, MHz$ to $12\, MHz$ band. The corresponding wavelength band is
A plane electromagnetic wave travels in vacuum along z-direction. If the frequency of the wave is $40 \,MHz$ then its wavelength is
A short bar magnet has a magnetic moment of $0.48\, J\, T^{-1}$. The magnitude and direction of magnetic field produced by the magnet at a distance of $10 \,cm$ from the centre of the magnet on its axis is

An electric dipole with dipole moment \(4 × 10^{−9} Cm\) is aligned at \(30^0\) with the direction of a uniform electric field of magnitude \(5 × 10^4 N C^{−1}\) Calculate the magnitude of the torque acting on the dipole.

A system has two charge s \(q_A = 2.5 × 10^{−7} C\) and \(q_B = −2.5 × 10^{−7 }C\) located at points A: (0, 0, − 15 cm) and B: (0, 0, + 15 cm), respectively. What are the total charge and electric dipole moment of the system?
Two point charges \(q_A = 3µC\) and \(q_B = −3µC\) are located 20 cm apart in vacuum. 
(a) What is the electric field at the midpoint O of the line AB joining the two charges? 
(b) If a negative test charge of magnitude \(1.5 × 10^{−9} C\) is placed at this point, what is the force experienced by the test charge?
When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.
The electrostatic force on a small sphere of charge 0.4 µC due to another small sphere of charge − 0.8 µC in air is 0.2 N.
(a) What is the distance between the two spheres?
(b) What is the force on the second sphere due to the first?
Dimensional formula of Stefan's constant is
Electric flux at a point in an electric field is
A particle is moving along a straight line path according to the relation $s^2 = at^2 + 2bt + c$ s represents the distance travelled in t seconds and a, b, c are constants. Then the acceleration of the particle varies as.
A steel wire of length $l$ has a magnetic moment $M$. It is then bent into a semicircular arc. The new magnetic moment is
On an open ground, a motorist follows a track that turns to his left by an angle of $60^?$ after every $500\,m$. Starting from a given turn, the displacement of the motorist at the third turn is