Physics Class 12th Practical Viva Questions with Answers in English Medium

Practical Examination

Before questioning examiner will check?

  • Practical record
  • How many syllabuses you have covered?

Physics practical

What kind of Viva questions are asked on the NIOS practical exams?

Type 1: – Examiner have asked (Based 12th student knowledge).

  • What is the total focal length and power of a combination of n lenses?

Let f1​, f2​ and f3​ be three focal lengths of the lenses.
Combined Focal length

Power of n lenses: – P = P1 + P2 + P3 +…+ Pn

  • Differentiate between emf and potential difference?
  • What happens if we place concave lens in water?

Ans: When concave lens immersed in water the focal length of lens increases because focal length of lens is directly proportional to refractive index of medium and when immersed in water the medium become more dancer so its focal length increases.

  • Why is a meter bridge called so? State it’s principle?

Ans: The reason why this bridge is called the Meter Bridge is because of the fact that it works on the Wheatstone bridge’s principle. So, people also popularly call it Wheatstone’s meter bridge. Another thing is that the wire length used in this circuit is 1 meter, so it has got its name as a meter bridge.

Principle of meter bridge: – Meter Bridge works on the principle of Wheatstone Bridge.

  • What is the total magnification of a combination of lenses?

Ans: Total magnification of n lenses = m1×m2×m3⋯×mn

  • How do you differentiate between a concave and convex lens without touching?

Ans: concave lens a lens that is thinner in the middle then at the diverges the incident ray away from its principal axis.

convex lens a lens that is thicker in the middle then at the converges the incident rays towards its principal axis

  • Which lens is used in vehicles? Why.

Ans:  Convex mirrors provide a wider view, the objects that are reflected in the mirror are diminished thus large number of objects can be seen this is the main reason for employing convex mirrors in automobiles.

  • What do you mean by power of lens?

Ans: The ability of a lens to bend the light rays is called power of lens. A convex lens converge the light rays towards the principal axis whereas a concave lens diverges the light rays away from the principal axis. In this way a lens bends the light rays.

Formula, P = 1/f

Type 2 : Chapter you have prepared?

Current electricity:

  • What is drift velocity?

Ans: The average velocity attained by charged particles, such as electrons, in a material due to an electric field

  • What is emf?

Ans: Electromotive force is defined as the electric potential produced by either electrochemical cell or by changing the magnetic field.

  • What is potential difference?

Ans: The work that has to be done in transferring unit positive charge from one point to the other, measured in volts.

  • Relation between drift velocity and torque (Relaxation time).

Ans: The drift velocity is the average velocity of the charge that resides in the conductor. So we can say that the drift velocity is directly proportional to the relaxation time, which means as the drift velocity increases relaxation time also increases and vice versa reason being the charge carries have more time to accelerate between collisions.

Q1. The least count of Vernier Calliper?

 Ans. 0.Olcm

Q2. The least count of Screw gauze? 

Ans. 0.001cm

Q3. State Ohms law? 

Ans. So long as the physical state of the conductor remains the same, the current through the conductor passed is directly proportional to the potential difference(V) between those terminals..

Q4. On which principle Sonometer experiment is based? 

Ans. Resonance.

Q5. Why we are putting the rubber pad inside the flask in the Resonance Tube experiment.? 

Ans. When a tuning fork, struck by a rubber pad, is held over a length of the air column in a tube, it produces a loud sound for a fixed length of the air column.

Q6. Why We use Vernier Calliper?

 Ans. It is used to measure the inner diameter of a solid sphere, the outer diameter of a solid sphere, and the depth of a cylinder.

Q7. Why We use Screw Gauze? 

Ans. It is used to measure the diameter of a cylindrical wire that means a metal normal copper wire or else metal wire.

Q8. Hooke’s Law? 

Ans. Within elastic limit, stress given to a body is directly proportional to strain observed in the body, or simply you can say stress is directly proportional to strain.

Q9. S.1 Unit for Frequency? 

Ans. Hertz(Hz).

Type 3 : Devices based questions

  • Principle
  • Conceptual questions based on working.

Galvanometer, cyclotron, meter bridge, potentiometer, transformer, Rectifier, Zener diode, Solar cell and P-N Junction.

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