Home
Class 12
PHYSICS
Given reasons for the following : (i) ...

Given reasons for the following :
(i) High reverse voltage do not appear across a LED.
(ii) Sunlight is not always required for the working of a solar cell.
(iii) The electric field, of the junction of a Zener diode, is very high even for a small reverse bias voltage of about 5 V.

Text Solution

Verified by Experts

(i) Because of its heavy doping as reverse voltage is applied minority carriers increases near junction and current starts flowing.
(ii) Because energy produced by solar cell can be stored in batteries for later use, when sunlight is not available.
(iii) As the depletion width si very small `(lt10^(_7))` even a small voltage say 5V can set up a very high electric field as `E=(V)/(d)`.
Promotional Banner

Topper's Solved these Questions

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise SECTIONS-D|4 Videos

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise SECTIONS-E|4 Videos

  • XII BOARDS

    XII BOARDS PREVIOUS YEAR|Exercise SECTIONS-B|6 Videos

  • SAMPLE PAPER 2019

    XII BOARDS PREVIOUS YEAR|Exercise SECTION D|6 Videos

Similar Questions

Explore conceptually related problems

Give reasons for the following: (i) High reverse voltage do not appear across a LED. (ii) Sunlight is always required for the working of a solar cell. (iii) The electric field, of the junction of a ener diode, is very high even for a small reverse bias voltage of about 5V.

The reverse breakdown voltage of a Zener diode is 5.6 V in the given circuit then I_z in mA is ___________

Read the following text and answer the following questions on the basis of the same: Light Emitting Diode: It is a heavily doped p-n junction which under forward bias emits spontaneous radiation. The diode is encapsulated with a transparent cover so that emitted light can come out. When the diode is forward biased, electrons are sent from n to p (where they are minority carriers) and holes are sent from p to n(where they are minority carriers). At the junction boundary, the concentration of minority carriers increases as compared to the equilibrium concentration (i.e., when there is no bias). Thus at the junction boundary on either side of the junction, excess minority carriers are there which recombine with majority carriers near the junction. On recombination, the energy is released in the form of photons. Photons with energy equal to or slightly less than the band gap are emitted. When the forward current of the diode is small, the intensity of light emitted is small. As the forward current increases, intensity of light increases and reaches a maximum. Further increase in the forward current results in decrease of light intensity. LED's are biased such that the light emitting efficiency is maximum. The V-I characteristics of a LED is similar to that of a Si junction diode. But, the threshold voltages are much higher and slightly different for each colour. The reverse breakdown voltages of LED's are very low, typically around 5 V. So care should be taken that high reverse voltages do not appear across them. LED's that can emit red, yellow, orange, green and blue light are commercially available. The reverse breakdown voltages of LED's are:

In the case of a p-n junction diode, if the reverse bias is very high, there is a sudden large increase in current. In this case the value of reverse bias voltage is known as

Consider the following statements A and B and identify the correct answer (A) A Zener diode is always connected in reverse bias to use it as voltage regulator. (B) The potential barrier of a p-n junction lies between 0.1 to 0.3 V , approximately.

Zener diode is a specially desined p-n junction diode, in which both p-side and n-side of p-n junction are heavily doped. The zener diode is designed especially to operate in the reverse break down voltage region continuosly without being damaged? Zener diode is used to remove the fluctuations from the given voltage and thereby provides a voltage of constant magnitude (i.e., Zener diode is used as voltage regulator). Read the above pragraph and answer the following question: (i) What is the most important use of Zener diode? (ii) What are the essential conditions for proper working of Zener diode? (iii) What do you learn from the above atudy?