List of top Physics Questions

A galvanometer of resistance \( G \) is shunted by a resistance \( S \, \Omega \). To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is
Three charges, each \( +q \), are placed at the corners of an isosceles triangle ABC of sides BC and AC, 2a. D and E are the mid-points of BC and CA. The work done in taking a charge \( Q \) from D to E is
A transistor is operated in common emitter configuration at \( V_C = 2V \) such that a change in the base current from 100 μA to 300 μA produces a change in the collector current from 10 mA to 20 mA. The current gain is
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron
Charge \( q \) is uniformly spread on a thin ring of radius \( R \). The ring rotates about its axis with a uniform frequency \( f \). The magnitude of magnetic induction at the centre of the ring is
If a triode value amplification factor is 20 and plate resistance is \( 10 \, \text{k}\Omega \), then its mutual conductance is
The current in a coil varies with time as shown in the figure. The variation of induced emf with time would be
Calculate the energy released when three \( \alpha \)-particles combined to form a \( \text{C}^{12} \) nucleus, the mass defect is
The output wave form of full-wave rectifier is
In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is
In photoelectric emission, the current varies with time as shown. The variation of induced emf with time would be
In the figure shown, the magnetic field induction as the point \( O \) will be
Each resistance shown in figure is \( 2 \, \Omega \). The equivalent resistance between A and B is
The turn ratio of transformers is given as 2:3. If the current through the primary coil is 3A, thus calculate the current through load resistance.
In an AC circuit, the potential across an inductance and resistance joined in series are respectively 16V and 20V. The total potential difference across the circuit is
Highly energetic electrons are bombarded on a target of an element containing 30 neutrons. The ratio of radius of nucleus to that of Helium nucleus is (14)³. The atomic number of nucleus will be
If hydrogen atom is its ground state absorbs \( 10.2 \, \text{eV} \) of energy. The orbital angular momentum increases by
In hydrogen atom, an electron is revolving in the orbit of radius 0.53 Å with \( 6.6 \times 10^{15} \) radiations. Magnetic field produced at the centre of the orbit is
The dipole moment of the short bar magnet is \( 12.5 \, \text{A} \cdot \text{m}^2 \). The magnetic field on its axis at a distance of \( 0.5 \, \text{m} \) from the centre of the magnet is
Charge passing through a conductor of crosssection area \( A = 0.3 \, \text{m}^2 \) is given by \( q = 3t^2 + 5t + 2 \, \text{C} \), where \( t \) is in seconds. What is the value of drift velocity at \( t = 2 \) seconds?
In a hydrogen discharged tube it is observed that through a given cross-section \( 3.13 \times 10^{15} \) electrons are moving from right to left and \( 3.12 \times 10^{15} \) protons are moving from left to right. What is the electric current in the discharge tube and what is its direction?
A hollow conducting sphere is placed in an electric field produced by a point charge at \( P \) as shown in figure. Let \( V_A \), \( V_B \), \( V_C \) be the potentials at points A, B, and C respectively. Then
Two capacitors of capacitance \( 1 \mu F \) and \( 2 \mu F \) are connected in series and the combination is charged to a potential difference of 120 V. If the charge on the combination is 80 μC, the energy stored in the capacitor of capacitance \( C_1 \) is
A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is
A direct X-ray photograph of the intensities is not generally taken by radiologists because