Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%

A source of ac voltage v = v₀ sin ωt, is connected across a pure inductor of inductance L. Derive the expressions for the instantaneous current in the circuit. Show that average power dissipated in the circuit is zero.

Show that Lenz's law is a consequence of conservation of energy.

An electron jumps from fourth to first orbit in an atom. How many maximum number of spectral lines can be emitted by the atom? To which series these lines correspond?

The carrier wave is represented by

The carrier wave of a signal is given by C(t) = 3 sin (8πt) volt. The modulating signal is a square wave as shown. Find its modulation index.

In both β⁻ and β⁺ decay processes, the mass number of a nucleus remains the same, whereas the atomic number Z increases by one in β⁻ decay and decreases by one in β⁺ decay. Explain giving reason.

Define the term modulation. Draw a block diagram of a simple modulator for obtaining AM signal ?

In a series LCR circuit, obtain the condition under which the impedance of the circuit is minimum ?

In a series LCR circuit, obtain the condition under which watt-less current flows in the circuit ?

In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their function.

Predict the directions of induced currents in metal rings 1 and 2 lying in the same plane where current I in the wire is increasing steadily.

The figure shows a series LCR circuit with L = 10.0 H, C = 40 μF, R = 60 Ω connected to a variable frequency 240 V source, calculate

(i) the angular frequency of the source which drives the circuit at resonance,

(ii) the current at the resonating frequency,

(iii) the rms potential drop across the inductor at resonance.

Predict the direction of induced current in a metal ring when the ring is moved towards a straight conductor with constant speed v. The conductor is carrying current I in the direction shown in the figure.

Predict the direction of induced current in metal rings 1 and 2 when current I in the wire is steadily decreasing?

A bar magnet is moved in the direction indicated by the arrow between two coils PQ and CD. Predict the directions of induced current in each coil.

In the given block diagram of a receiver, identify the boxes labeled as X and Y and write their functions.

A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit. Plot a graph to show the variation of current with frequency of the source, explaining the nature of its variation.

Draw a plot of potential energy of a pair of nucleons as a function of their separations. Mark the regions where the nuclear force is (i) attractive and (ii) repulsive.