List of practice Questions

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

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

If hydrogen atom is its ground state absorbs \( 10.2 \, \text{eV} \) of energy. The orbital angular momentum increases by

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

Each resistance shown in figure is \( 2 \, \Omega \). The equivalent resistance between A and B 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

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?

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 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

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?

In CuSO₄ solution when electric current equal to 2.5 Faraday is passed, the gram equivalent deposited on the cathode is

The potential of a large liquid drop when eight liquid drops are combined is 20V. Then the potential of each single drop was

A and B are two metals with threshold frequencies \( 1.8 \times 10^{14} \, \text{Hz} \) and \( 2.2 \times 10^{14} \, \text{Hz} \). Two identical photons of energy \( 0.825 \, \text{eV} \) each are incident on them. Then photoelectrons are emitted by (Take \( h = 6.6 \times 10^{-34} \, \text{J.s} \)):

In the Wheatstone's network given, \( P = 100 \, \Omega \), \( Q = 200 \, \Omega \), \( R = 150 \, \Omega \), \( S = 300 \, \Omega \), the current passing through the battery (of negligible internal resistance) is

Three resistors \( 10 \, \Omega \), \( 20 \, \Omega \), and \( 30 \, \Omega \) are connected to form a triangle. Across \( 30 \, \Omega \) resistor a 3V battery is connected. The current through \( 30 \, \Omega \) resistor is

In a common emitter amplifier the input signal is applied across

The kinetic energy of an electron get tripled then the de-Broglie wavelength associated with it changes by a factor

The threshold frequency for a photo-sensitive metal is \( 3.3 \times 10^{14} \, \text{Hz} \). If light of frequency \( 8.2 \times 10^{14} \, \text{Hz} \) is incident on this metal, the cut-off voltage for the photo-electric emission is nearly

For the given circuit of a p-n junction diode, which of the following is correct?

If the binding energy per nucleon in \( \text{Li}^7 \) and \( \text{He}^4 \) nuclei are respectively \( 5.60 \, \text{MeV} \) and \( 7.06 \, \text{MeV} \), then the energy of the reactor \[ \text{Li}^7 + p \to \text{He}^4 + 2e \] is

The graph between the square root of the frequency of a specific line of the characteristic spectrum of X-ray and the atomic number of the target will be

A resistor \( R \), an inductor \( L \), and a capacitor \( C \) are connected in series to an oscillator of frequency \( n \). If the resonant frequency is \( n_r \), then the current lags behind voltage when

A parallel plate capacitor has capacitance \( C \). If it is equally filled the parallel layers of materials of dielectric constant \( K_1 \) and \( K_2 \), its capacity becomes \( C_T \). The ratio of \( C_T \) and \( C \) is