SYJC Physics Practicals 

Important Viva Questions

(Developed and Maintained by Prof. Mukesh N Tekwani)

This is only a suggestive list of questions that may be asked in the Physics Viva exam. Students should note that they may be asked other questions as well, based on the syllabus of Physics.

These viva questions are common to main practical and activities.

This list will be updated periodically and so the student should visit this page regularly. 

(Developed and Maintained by Prof. Mukesh N. Tekwani)

For each experiment, remember to do this:

1. Write the final result at the end. Remember to give proper unit for the physical quantities.
2. If you are asked to draw a graph, remember these points:

• Give title of the graph, for example: Graph of n vs 1/L. Title should specify the quantity on the Y-axis vs the quantity on the X-axis
• Give scale on right hand side top corner.
• Draw the axes and label them with proper unit.

Common questions for all experiments:

1. What is the aim of the experiment you are performing?
2. Name the apparatus provided to you for this experiment.
3. What is the principle of working of this experiment?
4. In which chapter in your syllabus have you come across this topic? 
5. What is the least count of the measuring instrument(s) supplied to you?
6. What precautions will you take in performing this experiment?

Spring - Mass Oscillator

1. Define force constant or spring constant of a spring. 
• The force required to produce a unit extension (say, 1 cm) is called the force constant of the spring.
2. The spring constant of a spring is 200 N/m. What does it mean?
• It means that a force of 200 N is required to stretch the spring by 1 m.
3. What is the principle of a spring?
• It depends on the principle of Hooke's Law which states that the extension produced is directly proportional to the force applied within elastic limit.
4. Does the thickness of the material of the spring affect its spring constant? How?
• Yes, the thickness affects the spring constant. Thicker the wire, more is the spring constant.
5. Define time period of oscillation. 
• The time required to complete one oscillation is called the time period. 
6. Define the term "turn density" of a spring.
• Turn density of a spring is defined as the number of turns per unit length.
7. What is the MKS or SI unit of force constant? 
• MKS unit of force constant is N/m
8. Does a spring obey Hooke's law? 
• Yes a spring obeys Hooke's law upto the elastic limit.
9. Under what conditions will a spring obey Hooke's Law? 
• Extension of the spring should be within elastic limits.
10. Define the term "oscillation".
• The to-and-fro motion of a particle about a mean position is called oscillation.
11. What is the unit of mass?
• Unit of mass in MKS system is kilogram and in CGS system it is grams.
12. What is the unit of weight?
• Unit of weight in MKS system is Newton (N0 and in CGS system it is dynes. 
13. Is mass same as weight?
• No, mass and weight are not the same. 
14. What is the difference, if any, between mass and weight?
• Mass of a body is constant but weight of a body depends on the acceleration due to gravity at the place. Weight changes from place to place.
15. How will you convert mass of a body into its weight?
• weight = mass x gravitational acceleration i.e., weight W = mass (M) x g precautions will you take in performing this experiment?

Surface Tension

1. Define surface tension.
2. What are the factors affecting surface tension?
3. What is the CGS unit of surface tension?
4. What is the MKS unit of surface tension?
5. Define the term "least count of a measuring instrument".
6. For tap water and clean glass, what is the angle of contact?
7. Why is a travelling microscope called so?
8. What is a capillary tube?
9. Define the term "capillarity"
10. What are the different parts of the travelling microscope?
11. What is the effect on surface tension if soap or detergent is added to water?
12. What is the effect of temperature on surface tension?
13. What are cohesive and adhesive forces?
14. Why is the free surface of water concave but that of mercury is convex? or Why liquid surfaces are curved?
15. Define angle of contact.
16. In which case is the angle of contact (a) zero, (b) acute, and (c) obtuse 
17. What precautions will you take in performing this experiment?

Newton's Law of Cooling

1. State Newton's law of cooling.
• The rate of cooling of a body is directly proportional to the difference of temperature of the body and the surroundings, provided the excess is small.
2. What is the use of the stirrer in this experiment?
• Due to stirring, the temperature of water in the calorimeter remains uniform.
3. What is the effect of area of cross-section on rate of cooling?
• As the area of cross-section increases, rate of cooling also increases. Example: tea cools faster in a saucer than in a cup.
4. State the three modes of transfer of energy.
• The three modes of transfer of energy are: radiation, conduction and convection.
5. How will you determine the room temperature just now?
• The room temperature can be determined by using the thermometer.
6. What is the least count of the thermometer given to you?
• The least count of the given thermometer is _____ (write the value for your thermometer) 
7. What is the least count of the stop clock/ stop watch given to you? 
• The least count of the given clock/watch _____ (write the value for your thermometer) 
8. What is the liquid used in the thermometer provided to you?
• The liquid used in the thermometer is mercury.
9. What is the purpose of the plane mirror provided to you?
• The plane mirror is used to find the slope of the curve at a particular temperature.
10. Why do we draw tangents to the curve at various places to find the rate of cooling? Why not just find the slope of the curve?
• The slope of a curve is different at different points. So we must first draw a tangent to the curve at different points, and then find the slopes of the tangents.

Sonometer - I and II

1. State the law of length.
• The frequency of vibration of a wire of finite length, fixed at its ends, and under a tension, is inversely proportional to the length of the wire.
2. State the law of tension.
• The frequency of vibration of a wire of finite length, fixed at its ends, and under a tension, is directly proportional to the square root of the tension.
3. Define the term "frequency". State the unit of frequency.
• The number of vibrations per second is called frequency. Unit of frequency is Hertz (Hz).
4. Define the term "linear density" Is it the same as "mass per unit length"? 
• Linear density is defined as the mass of unit length of a wire or a string. Yes, it is the same as mass per unit length.
5. State the MKS unit of "linear density" or mass per unit length.
• MKS Unit of linear density is kg / m
6. What is a stationary wave?
• When two waves of equal frequency, equal amplitude, travelling with the same speed in opposite directions superimpose, a new type of wave is created - this is called a stationary wave.
7. Define node and antinode. 
• Node is point of minimum displacement or maximum pressure. Antinode is point of maximum displacement or minimum pressure.
8. What part do the bridges play in this experiment?
• Bridges reflect the waves at the ends and produce stationary waves.
9. Define tension. What are the SI and CGS units of tension? 
• Force acting in a string or a wire is  called tension. SI unit of tension is N and CGS unit of tension is dyne.
10. Which instrument is used in the laboratory to produce a tone?
• A tuning fork is used to produce a tone of a fixed frequency.
11. What is a tuning fork?
• It is an instrument used to produce a sound note of a fixed frequency.
12. What is resonance?
• When the frequency of the applied periodic force (by the tuning fork) becomes equal to the natural frequency of the wire, resonance is said to occur.
13. What is the frequency of vibration of the wire at resonance?
• At resonance, the frequency of vibration of the wire is equal to the frequency of the tuning fork.

Resonance Tube

1. What is resonance?
• When the frequency of the applied periodic force (by the tuning fork) becomes equal to the natural frequency of the air column, resonance is said to occur, and a loud sound is heard.
2. What is the CGS unit of speed of sound?
• CGS speed of sound is m/s or metre per second.
3. When you place a vibrating tuning fork on the mouth of a resonance tube, what is vibrating inside the resonance tube?
• When you place a vibrating tuning fork on the mouth of a resonance tube, an air column is vibrating.
4. What is the relation between frequency and resonating length?
• Resonating length is inversely proportional to frequency. 
5. What is end-correction? Why is it necessary?
• The antinode is not formed at the open end of the resonance tube, but is formed at a distance 0.3d above the open end. This correction is called the end correction. and it is necessary because the wave spreads out slightly above the open end.
6. How will the frequency of a tuning fork change (increase or decrease) if it is filed a little?
• The frequency of the tuning fork will increase if it is filed a little.
7. How will the frequency of a tuning fork change (increase or decrease) if it is loaded with wax?
• The frequency of the tuning fork will decrease if it is loaded with wax.
8. Which of these travels faster through air: sound or light?
• Light travels faster through air.
9. What is the speed of light in MKS system? 
• Speed of light in air is approximately 3 x 10⁸ m/s
10. What is the speed of sound in air at room temperature?
• Speed of sound in air, at room temperature is approx. 331 m/s
11. Can anything travel faster than speed of sound? 
• Yes, certain planes can travel faster than speed of sound and these are called supersonic planes.

Laws of Resistances Using Metre Bridge

1. Why is a metre bridge called so?
• The length of the wire fitted in the apparatus is one metre and so it is called a metre bridge. Also, there are two gaps - a left gap and a right gap, and these gaps must be bridged by some device like a resistance.
2. State the law of series resistances.
• When a number of resistances are connected in series, the total resistance is the sum of the individual resistances. R = R₁ + R₂ + R₃
3. State the law of resistances in parallel.
• When a number of resistances are connected in parallel, the reciprocal of total resistance is the sum of the reciprocals of the individual resistance. 1/R =  1/R₁ + 1/R₂ + 1/R₃
4. State Ohm's law.
• If the physical state of a conductor remains constant, the current flowing through a resistance is directly proportional to the applied voltage.
5. Which instrument is used in this experiment to detect current?
• A galvanometer is used to detect current.
6. Is a galvanometer a current measuring or current detecting instrument?
• A galvanometer is a current detecting instrument. 
7. What is the unit of electric current?
• Unit of electric current is ampere.
8. What is the unit of resistance?
• Unit of resistance is ohm.
9. Define electric current.
• Electric current is defined as the number of electrons flowing past a given point in unit time.
10. Define resistance.
• Opposition offered to the flow of electric current is called resistance.
11. What is the difference between battery and cell?
• A number of cells connected together is called a battery.
12. Draw the circuit symbol of resistance.

13. Draw the circuit symbol of rheostat.

Potentiometer

1. What is the principle of potentiometer?
2. Define the term potential difference.
3. What is the unit of potential?
4. What is the unit of potential difference?
5. Identify the Daniel and Leclanche cells.
6. What is the length of the potentiometer wire?
7. Which has more resistance - galvanometer or ammeter?

PN Junction Diode

1. What is pn junction diode?
• A pn junction diode is an electronic semiconductor device  formed by p and n-type semiconductors. 
2. State any one application/use of pn junction diode.
• PN junction diode is used to rectify alternating current to direct current.
3. What is meant by forward-biased diode?
• When the p-type semiconductor is connected to the positive terminal of a cell and n-type semiconductor is connected to the negative terminal of the cell, the pn-junction diode is said to be forward biased.
4. What is meant by reverse-biased diode?
• When the p-type semiconductor is connected to the negative terminal of a cell and n-type semiconductor is connected to the positive terminal of the cell, the pn-junction diode is said to be reverse biased.
5. Identify the anode and cathode of the diode given to you.
• There is a ring at the cathode 
6. What is meant by "potential divider circuit"? Identify the potential divider circuit in this circuit diagram.
• The rheostat is used to create a potential divider circuit in this experiment.

Wheatstone's Metre Bridge - Resistance of a  Wire

1. What is the principle of this experiment?
2. Define specific resistance.
• Specific resistance is defined as the resistance of a conductor of unit length and unit area of cross-section. It is also called resistivity. 
3. What is the unit of specific resistance?
• Unit of specific resistance is ohm m
4. Identify (give names of) all the equipment supplied to you for this experiment.
• Galvanometer, cell, rheostat, jockey, metre bridge, plug key, resistance wire, connecting wires.
5. Give the purpose of all the apparatus supplied to you.
• Galvanometer - to detect current
• Cell/power supply - to supply an electric current in the circuit
• Resistance box - to vary the resistance in one arm of the Wheatstone bridge.
6. What is the least count of the scale supplied to you on Wheatstone's metre bridge?
• Least count of the scale is 1 mm or 0.1 cm.
7. What is the purpose of the plug key in this experiment?
• Purpose of the plug key is to stop / start the flow of current in the circuit.

Resistance of Galvanometer

1. What is a galvanometer used for?
• It used to detect current.
2. What is meant by resistance?
• Resistance is the opposition offered to the flow of electric current.
3. What is meant by resistance of  galvanometer?
• It is the resistance of the coil of the galvanometer.
4. What is the principle of working of this experiment?
• It is based on the principle of Wheatstone's bridge.
5. What is the unit of resistance?
• Unit of resistance is ohm.
6. How will you convert a galvanometer into an ammeter?
• A galvanometer is converted into an ammeter by connecting a high resistance in series with the galvanometer coil.
7. How will you convert a galvanometer into a voltmeter?
• A galvanometer is converted into a voltmeter by connecting a low resistance in parallel with the galvanometer coil.

Internal Resistance of a Cell

1. What is meant by internal resistance of a cell?
2. Why does a cell have internal resistance?
3. There are two cells, one with a high internal resistance and the other with a low internal resistance. Which cell is better? Why?
4. Name the cell that you are using in this experiment.
5. What is the difference between a battery and a cell?

Simple Pendulum - Dissipation of Energy

1. What is a simple pendulum?
2. Define time period of a simple pendulum.
3. What is the unit of time period?
4. Define one oscillation.
5. What is meant by "dissipation" of energy?
6. What will be the nature of the graph you have to plot in this experiment?
7. How will the amplitude of oscillation change with time?
8. Does the time period of a simple pendulum depend on the mass of the bob?
9. What are the factors on which the time period of the simple pendulum depend?
10. Does a stop watch / stop clock have a least count?
11. Define least count of a measuring instrument.
12. What is the least count of the stop clock / stop watch supplied to you.
13. What is the least count of the watch you are wearing?  OR What is the least count of the clock in your physics laboratory?
14. Does every measuring instrument have a least count?

Identification of Components / Use of Multimeter 

1. Name each electronic component supplied to you.
2. What is the use of resistor?
3. What is the color code of resistor?
4. Name any one electronic device that uses a resistor.
5. What is the use of a diode?
6. What are the two terminals of a diode called?
7. Identify the anode and cathode of a diode.
8. What is a transistor used for? OR Give one application of transistor?
9. What are the three terminals of a transistor called?
10. What is the full form of the term LED?
11. When does a LED emit light?
12. How many terminals does a LED have?
13. Name any one device that uses a LED.
14. What is an integrated circuit? What is the full form of IC?
15. What is the significance / importance / meaning of the word "integrated" in the term "integrated circuit"?
16. Name any two electronic devices  which use an IC.
17. What is the function of a capacitor?
18. What is the unit of capacitance?
19. What is a multimeter used for?
20. Why is a multimeter called a "multi"meter?

Fault Finding in an Electrical Circuit 

1. How is a voltmeter connected to measure the voltage across a resistance?
• A voltmeter is always connected in parallel (across) with a resistance to measure the voltage.
2. How is an ammeter connected to measure the current through a resistance?
• An ammeter is always connected in series with a resistor to measure the current through it.
3. How many terminals does a rheostat have?
• A rheostat has three (3) terminals - two are fixed terminals at the bottom and one is a variable terminal at the top.
4. What is the purpose of a rheostat?
• A rheostat is used to change the current through a circuit or potential drop across a component.
5. Which two terminals of a rheostat must necessarily be connected to vary the current through the circuit?
• One fixed terminal and the variable terminal must always be connected to vary or change the current through the circuit.
6. Which two terminals of a rheostat must necessarily be connected to keep the current through the circuit constant?
• The two fixed terminals of the rheostat must be connected to keep the current through the circuit constant.
7. What is the function of the plug key in an electrical circuit?
• The plug key is used to stop the flow of current through a circuit; it acts like a switch.

Digital Circuits - Demonstration 

1. What is a logic circuit?
2. Name any three logic gates.
3. Explain the truth table of AND gate.
4. Explain the truth table of OR gate.
5. Explain the truth table of NOT  gate.
6. Explain the truth table of NAND gate.
7. Explain the truth table of NOR gate.

Melde's Experiment  - Demonstration 

1. What is a stationary wave?
2. Define the term "node".
3. Define the term "antinode". 
4. What is the unit of frequency?
5. What is the relation between number of loops and tension in the string?
6. Describe the parallel position in this experiment. Why is it called "parallel" position?
7. Describe the perpendicular position in this experiment. Why is it called "perpendicular" position?
8. What is meant by linear density of string?
9. What are the MKS and CGS units of linear density?
10. Is the apparatus arranged in parallel or perpendicular position? OR In which position is te apparatus arranged?

Light Dependent Resistor - LDR

1. What is the full form of LDR?
• LDR stands for Light Dependent Resistor.
2. What is a LDR?
• LDR is a device whose resistance decreases as the intensity of light falling on it increases.
3. What is the substance used to make an LDR?
• LDR is made up of semiconductor materials like cadmium sulphide (CdS).
4. What is the circuit symbol of LDR?
• Circuit symbol of LDR is  shown below