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

Correct expression for force on a current carrying conductor of length dl in a magnetic field is ______.

Thin lens approximation for a lens is ______.

An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

When a magnetic compass needle is carried nearby to a straight wire carrying current, then

1. the straight wire cause a noticeable deflection in the compass needle.
2. the alignment of the needle is tangential to an imaginary circle with straight wire as its centre and has a plane perpendicular to the wire.

A charged particle is moving on circular path with velocity v in a uniform magnetic field B, if the velocity of the charged particle is doubled and strength of magnetic field is halved, then radius becomes ______.

A small object with charge q and weight mg is attached to one end of a string of length ‘L’ attached to a stationary support. The system is placed in a uniform horizontal electric field ‘E’, as shown in the accompanying figure. In the presence of the field, the string makes a constant angle θ with the vertical. The sign and magnitude of q ______.

What happens during regulation action of a Zener diode?

1. The current in and voltage across the Zenor remains fixed.
2. The current through the series Resistance (R_s) changes.
3. The Zener resistance is constant.
4. The resistance offered by the Zener changes.

With the help of a neat circuit diagram, explain the working of a photodiode. 

Two parallel-plate capacitors X and Y have the same area of plates and same separation between them. X has air between the plates, while Y contains a dielectric medium of ε_r = 4.

(i) Calculate capacitance of each capacitor if the equivalent capacitance of the combination is 4 μF.

(ii) Calculate the potential difference between the plates X and Y.

(iii) Estimate the ratio of electrostatic energies stored in X and Y.

Meeta's father was driving her to school. At the traffic signal, she noticed that each traffic light was made of many tiny lights instead of a single bulb. When Meeta asked this question to her father, he explained the reason for this.

Answer the following questions based on above information:

(i) What were the values displayed by Meeta and her father?

(ii) What answer did Meeta's father give?

(iii) What are the tiny lights in traffic signals called and how do these operate?

How is a Zener diode fabricated?

Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.

If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is (i) forward biased

If a small voltage is applied to a p-n junction diode, how will the barrier potential be affected when it is(ii) reveres biased?

What should be the width of each slit to obtain 10 maxima of the double slit pattern within the central maximum of the single slit pattern, for green light of wavelength 500 nm, if the separation between two slits is 1 mm?

With what considerations in view, a photodiode is fabricated? State its working with the help of a suitable diagram.

Even though the current in the forward bias is known to be more than in the reverse bias, yet the photodiode works in reverse bias. What is the reason?