Photodiode

Q. When N-type of semiconductor is heated,

1. Number of electrons increases while that of holes decreases
2. Number of holes increases while that of electrons decreases
3. Number of electrons and holes remains same
4. Number of electrons and holes increases equally

Q.

What are the different types of a photodiode?

Q.

Is diode linear or nonlinear?

Q. Consider the following electronic energy level diagram of $H-$ atom. Photons associated with shortest and longest wavelengths would be emitted from the atom by the transitions labelled

1. $D$ and $C$ respectively
2. $C$ and $A$ respectively
3. $C$ and $D$ respectively
4. $A$ and $C$ respectively

Q. Which of the following energy band diagram shows the N-type semiconductor?

1. 
2. 
3. 
4. 

Q.

Why does the width of depletion region increase in reverse bias?

Q.

Light of frequency 3 times the threshold frequency is incident on photosensitive material. If the frequency is half and intensity is double . The photoelectric current becomes _____________

Q. In a PN junction photo cell, the value of photo-electromotive force produced by monochromatic light is proportional to

1. The frequency of the light falling on the cell
2. The voltage applied at the PN junction
3. The barrier voltage at the PN junction
4. The intensity of the light falling on the cell

Q. current in reverse bias is in microamperes while the current in forward bias is in milliamperes.Still, a photodiode is used in reverse bias.Why?

Q. Ultraviolet light of wavelength $300\text{nm}$ and intensity $1{\text{W/m}}^2$ falls on the surface of a photosensitive material. If one percent of the incident photons produce photoelectrons, then the number of photoelectrons emitted per second from an area of $1{\text{cm}}^2$ of the surface is nearly

1. $1.52\times {10}^{13}$
2. $1.51\times {10}^{12}$
3. $4.12\times {10}^{13}$
4. $2.13\times {10}^{11}$

Q.

Which of the following is an ohmic conductor?

1. LED

2. Thyristor

3. diode

4. Metal conductor

Q.

In a photodiode, the conductivity increases when the material is exposed to light. It is found that the conductivity changes only if the wavelength is less than 620 nm. What is the band gap ?

Q.

How does a mirror galvanometer work?

Q. The level formed due to impurity atom, in the forbidden energy gap, very near to the valence band in a p-type semiconductor is called -

1. accepter level.
2. donor level.
3. conduction level.
4. forbidden level.

Q. Light of frequency $3$ times the threshold frequency is incident on a photosensitive material. What will be the saturation photoelectric current, if the intensity is halved keeping frequency constant ?

1. Doubled
2. Halved
3. One fourth
4. Zero

Q. Comprehension :

A $100\Omega$ resistance is connected in series with a $4\text{H}$ inductor. The voltage across the resistor is, $V_R=2.0\sin \left({10}^{3}t\right)\text{V}.$

$\left(iii\right)$ Find amplitude of the voltage across the inductor.

1. 
   $40\text{V}$
2. 
   $60\text{V}$
3. 
   $80\text{V}$
4. 
   $90\text{V}$

Q. what is displacement current actually

Q.

Does current flow in reverse bias?

Q. In an electric iron heat produced is same, whether it is connected across an A.C. source or across 50 Vconstant voltage. R.M.S. value of the A.C. voltage applied is

Q.

In a potentiometer of one metre length, an unknown emf voltage source is balanced at 50 cm length of potentiometer wire while a 6 V battery is balanced at 30 cm length. The emf of unknown voltage source isOptions:Should have chosen

a)10 V

b) 6 V

c) 3 V

d) 9 V

Q. Symbolic representation of photodiode is

1. 
2. 
3. 
4. 

Q. The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current I of the photocell varies as follows:

1. 
2. 
3. 
4. 

Q. A photo diode measures ....... of light and is always operated in ........ biased configuration.

1. frequency, reverse
2. intensity, forward
3. frequency, forward
4. intensity, reverse

Q. Why is the photodiode always operated under reverse bias conditions ? What would happen if it were to be operated under forward bias conditions ?

Q. (a) In the following diagram 'S' is a semiconductor. Would you increase or decrease the value of R to keep the reading of the ammeter A constant when S is heated ?
Give reason for your answer.
(b) Draw the circuit of a photodiode and explain its working. Draw its I- V characteristics.

Q.

What is forward bias?

Q. Why is photodiode operated in the reverse bias?

Q. A p-n photodiode is fabricated from a semiconductor with band gapof 2.8 eV. Can it detect a wavelength of 6000 nm?

Q. In the following network of wires, the value of current $i$ is


$[$0.77 Mark$]$

1. $2\text{A}$
2. $3\text{A}$
3. $8\text{A}$
4. $6\text{A}$

Q. In the circuit shown in figure, the base current is, $I_B=10\mu \text{A}$ and the collector current is, $I_C=5.2\text{mA}$. The transistor is in which mode?

1. Active
2. Saturation
3. Cut-off
4. Inverted