Science (English Medium) Class 12 - CBSE Question Bank Solutions

If a constant force acts on a particle, its acceleration will ______________ .

A charged particle is projected at a very high speed perpendicular to a uniform magnetic field. The particle will _____________ .

A particular particle created in a nuclear reactor leaves a 1 cm track before decaying. Assuming that the particle moved at 0.995c, calculate the life of the particle (a) in the lab frame and (b) in the frame of the particle.

An ac circuit as shown in the figure has an inductor of inductance L and a resistor or resistance R  connected in series. Using the phasor diagram, explain why the voltage in the circuit will lead the  current in phase.

The potential difference across the resistor is 160V and that across the inductor is 120V. Find the  effective value of the applied voltage. If the effective current in the circuit be 1.0 A, calculate the total impedance of the circuit.

What will be the potential difference in the circuit when direct current is passed through the circuit? 

Write the range of the wavelength of the following electromagnetic radiations:
(a) Infrared rays
(b) Ultraviolet rays
(c) γ -rays

Write one use of each of the above.

Define the term "Intensity" in the photon picture of electromagnetic radiation. 

Answer the following question.
Why a signal transmitted from a TV tower cannot be received beyond a certain distance? Write the expression for the optimum separation between the receiving and the transmitting antenna.

Identify the part of the electromagnetic spectrum used in (i) radar and (ii) eye surgery. Write their frequency range.

Answer the following question.
In a series LCR circuit connected across an ac source of variable frequency, obtain the expression for its impedance and draw a plot showing its variation with frequency of the ac source. 

Answer the following question.
What is the phase difference between the voltages across the inductor and the capacitor at resonance in the LCR circuit? 

Answer the following question.
Draw the diagram of a device that is used to decrease high ac voltage into a low ac voltage and state its working principle. Write four sources of energy loss in this device.  

Define the term: threshold frequency

Answer the following question.
Plot a graph of photocurrent versus anode potential for radiation of frequency ν and intensities I₁ and I₂ (I₁ < I₂).

Identify the part of the electromagnetic spectrum used in
(i) radar and
(ii) eye surgery. Write their frequency range.

On the basis of the graphs shown in the figure, answer the following questions :

(a) Which physical parameter is kept constant for the three curves?

(b) Which is the highest frequency among v₁, v_2, and v₃?

Write two distinguishing features of nuclear forces.

Name the radiation of the electromagnetic spectrum which is used for the following:

Radar and Give the frequency range.

Name the radiation of the electromagnetic spectrum which is used for the following:

To photograph internal parts of the human body and Give the frequency range