List of practice Questions

Draw a labelled diagram of a step-up transformer. Obtain the ratio of secondary voltage to primary voltage in terms of number of turns in the two coils.
The number of turns in the primary and the secondary coil of an ideal transformer are 100 and 5000 respectively. If 3.3 kW power is supplied to the transformer at 220 V, find (I) current in the primary coil, and (II) output voltage.
Explain the following statement giving reason :
An equipotential surface through a point is normal to the electric field at that point.
Explain the following statement giving reason :
When a dielectric is placed in an external electric field, the electric field inside the dielectric is less than that outside it.
Explain the following statement giving reason :
The potential difference between the plates of a charged parallel plate capacitor decreases when its plates are brought closer.
Obtain an expression for the work done to dissociate the system of three charges $q$, $-4q$ and $2q$ placed at the vertices A, B and C respectively of an equilateral triangle of side '$a$'.
Define the terms (I) resonant frequency, and (II) power factor of a series LCR circuit. For what value of the power factor will the power dissipated in the circuit be maximum ?
Two coils, one of radius $0.5\text{ cm}$ having $10$ turns and the other of radius $5\text{ cm}$ having $50$ turns are placed coaxially in air such that their centres are coincident. Calculate the magnetic flux through the smaller coil if the larger coil carries a current of $3\text{ A}$.
Two coils, one of radius $0.5\text{ cm}$ having $10$ turns and the other of radius $5\text{ cm}$ having $50$ turns are placed coaxially in air such that their centres are coincident. Calculate the mutual inductance of the two coils.
The figure given below shows three straight long parallel conductors kept in x-y plane, carrying currents 2I, I and 3I respectively as shown in figure. Find the magnitude and direction of net magnetic force acting on unit length of conductor 1, due to conductors 2 and 3.
A rectangular loop of sides $l$ and $b$ and resistance ‘R’ is kept in a region in which the magnetic field varies as $B = B_0 \sin \omega t$. Derive expression for the emf induced in the loop.
A rectangular loop of sides $l$ and $b$ and resistance ‘R’ is kept in a region in which the magnetic field varies as $B = B_0 \sin \omega t$. Find the effective value of current that flows in the loop.
What are X-rays ? How are they produced ? Give two uses of X-rays.
Distinguish between isotopes and isobars, giving one example for each.
Derive the relation between atomic mass unit (u) and electron volt (eV).
‘Current is a scalar quantity, although we represent current with an arrow.’ Explain.
Derive the balance condition of a Wheatstone Bridge.
In a single-slit diffraction experiment, light of wavelength $\lambda$ illuminates the slit of width ‘a’. The diffraction pattern is observed on a screen kept at a distance D from the slits. How is the linear width of central maximum affected when separation between the slit and the screen is decreased ?
A convex lens of refractive index $1.5$ has a focal length of $20\text{ cm}$ in air. Find its nature and focal length when it is immersed in a transparent liquid of refractive index $1.25$.
Differentiate between nuclear fission and nuclear fusion, giving one example for each.
With the help of a circuit diagram, explain the working of a full wave rectifier. Depict the input and output waveforms.
Explain how the dual aspect of matter is evident in the de Broglie relation.
Radiation of wavelength $\lambda$ is incident on a photosensitive surface. Find the de Broglie wavelength of electrons emitted from the surface. Assume that the work function of the surface is negligible.
The figure given below shows three straight long parallel conductors kept in x-y plane, carrying currents 2I, I and 3I respectively as shown in figure. Find the magnitude and direction of net magnetic field at a point on conductor 1.
Assertion (A) : The conductivity of an n-type semiconductor is higher than that of a p-type semiconductor at a given temperature.
Reason (R) : The electrons being in the conduction band in n-type semiconductor are more mobile than the holes in the valence band in p-type semiconductor.