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hall effect experiment viva questions pdf

MOST EXPECTED PHYSICS VIVA QUESTIONS FOR PHYSICS PRACTICAL
MOST EXPECTED PHYSICS VIVA QUESTIONS FOR PHYSICS PRACTICAL



EXPERIMENT : FOUR PROBE
1) Energy band gap?
2) Relation of resistivity and T?
(In case of metal and semi-conductor with reason)
3) Depletion layer?
4) N- and p- type semi-conductors example?


EXPERIMENT : I-H CURVE
1) Retentivity and its plot on I-H curve?
2) Solenoid?
3) What does I-H curve area imply?
4) Examples of para-, di- and ferromagnetic materials?
5) What if I-H curve is broad?
6) Magnetic meridian?

EXPERIMENT : PLANK’S CONSTANT
1) Filter?
2) Stopping voltage?
3) Work function?
4) Photon?
5) Photovoltaic cell and function?

EXPERIMENT : ENERGY BAND GAP
1) Value of current in forward and reverse biasing? (Ans: milliampere and microampere resp.)
2) Depletion layer?
3) Example of acceptor and donor atoms?
4) Majority charge carriers in n- and p- type semi-conductors?

EXPERIMENT : NEWTON’S RING
1) Formula for interference?
2) Factors on which diameter of newton’s ring depend?
3) What if white light is used instead of sodium light?
4) Why we use broad source?
5) If water is added to lens will diameter change?

EXPERIMENT : MAGNETIC FILED DUE TO CIRCULAR COIL

1) Magnetic meridian?
2) Commutator key?
3) Effect on B as distance increases?
4) Examples of para-, di- and ferromagnetic materials?
5) Biot-Savart law?
EXPERIMENT : DIFFRACTION GRATING
1) Grating element?
2) Diffraction angle : Red > = < Violet?
3) Sodium light is used instead of white light. Will spectrum appear?
4) Diffraction?
5) What is a and b?

EXPERIMENT: HALL-COEFFICIENT
1) If hall-coefficient is negative what does it indicate?
2) Significance of hall-coefficient. What information do we get?
3) Hall effect?
4) n- and p- type impurities?

PHYSICS EXPERIMENT 4

EXPERIMENT NO. 4

Object: - To study the Hall Effect and to calculate:-
(i) The Hall Coefficient RH
(ii) The concentration of charge carriers

Required Apparatus:- Power supply for electromagnets, Gauss meter with hall probes, p type Ge semiconductor on PCB, multimeter, electromagnets.

Theory: A current carrying conductor (semiconductor/metal) is placed in the magnetic field perpendicular to the direction of current; a voltage is developed across the conductor in a direction perpendicular to both the current and magnetic field. The effect is known is as Hall Effect. This effect is very useful in determining-
> The nature of charge carries e.g. whether semiconductor is on n-type or p-type
> Carrier concentration or the no. density of charge carries
> Mobility of charge carriers

Formula used
Hall Coefficient

Carrier Concentration
Procedure:-
(1) Connect one pair of contact of specimen on the opposite faces to the current source and other pair to the multimeter.
(2) Switch on the power supply of electromagnet and measure the magnetic flux density at the centre between the pole faces by placing
(3)Place the specimen at the centre between the pole faces such that the magnetic field is perpendicular to the strip.
(4) Pass the current (mA) from the current source through the specimen and measure the resulting hall voltage in the multimeter / milivoltmeter.
(5)Increase the current through the specimen gradually and measure the corresponding Hall voltages.
(6)The entire process can be repeated for different values of magnetic flux density. Find the mean of different RH

Hall Effect in a Semiconductor Description (SHE)

Note that there is NO eating or drinking in the 111-Lab anywhere, except in rooms 282 & 286 LeConte on the bench with the BLUE stripe around it. Thank You the Staff.
In general the Hall effect refers to the fact that a voltage can develop in a direction transverse to the current flow in a system of charged particles in a magnetic field, owing to the Lorentz force q(v x B).
The electrical resistance of conductors and non-conductors is relatively easy to describe conceptually and mathematically, and experiments illustrating these properties are easy to do. We are all familiar with Ohm's law, and with using dielectrics as insulators. The temperature dependence is nothing unusual. Semiconductors fall in between these two extremes, and their properties require some knowledge of condensed matter physics. The Hall effect illustrates the Lorentz force v X B. In this experiment you will measure the resistivity and the Hall coefficient as functions of the temperature, for an Al-doped germanium crystal. You will then determine the concentration of the free carrier. When a current is passed through a sample in the x-diredction the Lorentz force acting on the electric charges moving in a magnetic field B ( in Z) displaces some carriers in the y-direction. This causes an internal electric field EH which cancels the Lorentz force in the equilibrium case. You will use the Van der Pauw method of measuring a sample of arbitary shape using the computer running LabView to acquire these data. The temperature range of this experiment is 300K to 77K to 400K.