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The practical examinations are accompanied by viva voce by the external/internal examiner to ensure the genuineness of their work and to analyse the understanding of the subject by the students.
So it is important to prove yourself by performing well in the viva voce.
The following questions will be of some help to prepare well for it. Please remember that the questions following the first is based on your answer to the first question. (However, there are some examiners who come with some questions written on their diary or paper and blindly ask from them. For them, please prepare the questions which are printed on the practical manual.)
Questions based on screw gauge experiments
- Define leastcount of a screw gauge (more…)
- State the Principle of a potentiometer. (The students say that potential drop is proportional to length but the constant quantities are not mentioned)
- How can we increase the sensitivity of a potentiometer?
- Define figure of merit of a galvanometer.
- Which has more resistance – a galvanometer or a milliammeter?
- How does an LED emit light?
- What is the difference between an ordinary diode and an LED?
- Define principal axis of a convex lens?
- What happens to the focal length of a concave mirror if it is immersed in water?
- What are the factors affecting the internal resistance of a cell?
- What are the difference between primary and secondary cell?
- Why can’t we use a dry cell for starting a car?
- What happens to the resistivity of a wire when it is doublefolded?
- How does the resistance of a wire depend on its dimensions?
- Why are the resistances used in a resistance box is like 1,2,2,5,10,20,20,50,100,200,
- Why constantan or manganin wires are used for making the resistance coils in resistance box?
- What is a standard resistance?
- What are the characteristics of a standard resistance?
- What are the precautions to be observed while doing electricity experiments in general?
- What is a galvanometer?
- What is the resistance of an ideal ammeter?
- Why is ammeter always connected in series and voltmeter always connected in parallel?
- How can we convert a galvanometer into an ammeter or a voltmeter?
- What is shunt?
- What is AVO meter?
- What is the effect of temperature on the resistance of a conductor?
- Why does the resistance of a conductor increases with temperature, whereas that of a semiconductor decreases with temperature.
- What is conductance?
- What are non ohmic devices? give an example.
- What are superconductors?
- Define emf
- Why emf is said to be a misnomer?
- What happens if the battery used in the primary circuit of a potentiometer has less emf compared to the emf of the cell used in the secondary circuit?
- If you find that the galvanometer reading is shaky, what error can you expect?
- What do you mean by figure of merit of a galvanometer?
- Why a moving coil galvanometer is called so?
- What is the principle of a galvanometer?
(Assuming that the student was assigned the experiment “To determine the internal resistance of a cell using potentiometer“)
Examiner (E): What was the experiment allotted to you?
Students(S): Sir, I was assigned the experiment to determine the internal resistance of a primary cell using potentiometer.
E: OK, Tell me the principle of a potentiometer
Viva Voce is one one of the important factor which decides your overall score in Physics Practical examination.
The external examiner is not knowing what you are really. Viva Voce is the only means to have a direct interaction with you. Therefore your performance in viva has a direct impact on the marks you get in the Practical exam.
Here are some tips for you to excell
- Understand the basics. The various experiments you are assigned are based on certain fundamental principles. Understanding these fundamentals are very important.
- Boost your confidence: Present yourself in a pleasing manner and answer the questions confidently
- Prepare a list of all questions which can be asked from each of the experiments you did at school and also thoroughly revise the related theory part from text book.
The following books will be of great help.
(Dear visitors, you can add your suggestions and questions as comments to this post)
How to do calculation in the physics practical(capillary rise method)..how to measure the diameter of the capillary tube?
A Travelling Microscope
A travelling microscope is used to determine small distance to an accuracy of 0.001 cm. The measurement principle is based on the principle of vernier. In a typical travelling microscope, the main scale divisions are of magnitude 0.05 cm (0.5 mm) each and the vernier scale contains 50 divisions. This makes the Least Count to be 0.05/50 = 0.001 cm.
Determination of diameter
For determination of diameter of the capillary along the horizontal direction
Mount the capillary tube in horizontal direction in a stand with the help of a rubber cork to place and hold the capillary tube. Rotate the microscope so that it is horizontal and in line with the tip of the capillary tube.
Now looking through the microscope, turn the focussing screw to get a clear image of the capillary tube. Now adjust the microscope in such a way that the vertical crosswire coincides with the left end of the capillary tube.
Take the reading
In the horizontal scale, look the zero of the veriner, and find out the division on the main scale just before the zero mark. Note it as the MSR.
Now look carefully at the vernier. Any one of the fifty lines will come exactly in line with one of the lines of the main scale. That division on the vernier is the vernier scale reading. note it down in the observation table.
Now move the telescope horizontally to focus on the right end of the capillary tube. Again take the reading as before.
Repeat the experiment by moving the telescope vertically coinciding the horizontal crosswire with top and bottom and now the readings are taken on the vertical scale.
From the observations you will get two values of diameter, one for vertical and one for the horizontal.
Least count of the traveling microscope = …… cm