List of top Physics Questions

The force constant of weightless spring is 16 N/m. A body of mass 1.0 kg suspended from it is pulled down through 5 cm and then released. The maximum kinetic energy of the system (spring + body) will be:

A solenoid has an inductance of 60 H and a resistance of 30 ohm. If it is connected to a 100 V battery, how long will it take for the current to reach \( e^{-1} \) of its maximum value?

A coil having an area of \( 2 \, \text{m}^2 \) is placed in a magnetic field which changes from 1 Wb/m² to 4 Wb/m² in 2 seconds. The emf induced in the coil will be:

A 10 m long copper wire while remaining in the east-west horizontal direction is falling down with a speed of 5.0 m/s. If the horizontal component of the earth’s magnetic field \( B = 0.3 \times 10^{-4} \, \text{Wb/m}^2 \) the emf developed between the ends of the wires is:

At what temperature will the resistance of a copper wire become three times its value at 0°C? (Temperature coefficient of resistance for copper \( \alpha = 4 \times 10^{-3} /°C \))

In a neon discharge tube, \( 2.9 \times 10^{18} \, \text{Ne}^{+} \) ions move to the right each second while \( 1.2 \times 10^{18} \) electrons move to the left per second, electrons charge is \( 1.6 \times 10^{-19} \, \text{C} \). The current in the discharge tube is:

An electron is accelerated through a potential difference of 200 V. If \( e/m \) for the electron is \( 1.6 \times 10^{11} \, \text{C/kg} \), the velocity acquired by the electron will be:

For germanium crystal, the forbidden energy gap in joules is:

Water is falling on the blades of a turbine at a rate of 100 kg/s. If the height of the fall is 100 m, the power transferred to the turbine will be approximately:

A metre scale is standing vertically on the earth’s surface on one of its end. It now falls on earth without slipping. Find the velocity with which the free end of the scale strikes the earth. (\( g = 10 \, \text{m/s}^2 \))

In a step-up transformer the turn ratio is 1:2. A Leclanché cell (emf 1.5 V) is connected across the primary. The voltage across the secondary is:

How much energy will be necessary for making a body of 500 kg escape from the Earth? (\( g = 9.8 \, \text{m/s}^2 \), radius of the Earth \( = 6.4 \times 10^6 \, \text{m} \))

A 10 \(\mu\)F capacitor is charged to a potential difference of 50 V and is connected to another uncharged capacitor in parallel. Now the common potential difference becomes 20 V. The capacitance of second capacitor is:

If 10 percent of the current passes through a moving coil galvanometer of resistance 99 ohm. Then the shunt resistance will be:

The velocity of an electron in the second orbit of sodium atom (atomic number = 11) is \( v \). The velocity of an electron in its fifth orbit will be:

A heavy mass is attached to a thin wire and is whirled in a vertical circle. The wire is most likely to break:

The molar heat capacity of rock salt at low temperature varies with temperature according to Debye's \( T^3 \) law. Thus \( C = k \frac{T^3}{\theta^3} \) where \( k = 1940 \, \text{Jmol}^{-1} \text{K}^{-1} \) and \( \theta = 281 \, \text{K} \). Calculate how much heat is required to raise the temperature of 2 moles of rock salt from 10 K to 50 K:

A charged particle enters a magnetic field \( H \) with its initial velocity making an angle of \( 45^\circ \) with \( H \). The path of the particle will be:

The time taken by AC of 50 Hz in reaching from zero to the maximum value is:

A p-type semiconductor has acceptor levels 57 meV above the valence band. The maximum wavelength of light required to create a hole is:

A force of 10 N acts on a body of mass 20 kg for 10 s. Change in its momentum is:

In which case does the potential energy decrease?

In an explosion, a body breaks into pieces of unequal masses. In this case:

A fish at a depth of 12 cm in water is viewed by an observer on the bank of a lake. To what height the image of this fish is raised? (Refractive index of lake water \( n = \frac{4}{3} \))

In Millikan’s oil drop experiment, an oil drop carrying a charge \( Q \) is held stationary by a potential difference 2400 V between the plates. To keep a drop of half the radius stationary, the potential difference had to be made 600 V. What is the charge on the second drop?