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## Class XII Physics MCQ for online tests

With teaching taking place mostly online due to Covid-19 threat, MCQ based assessment has become more popular. Here you can download Class XII Physics MCQ for online as well as offline testing. The materials may also be useful for JEE and NEET.

# Plus Two Physics Oral Test series

Many schools have started oral questioning also as part of diagnostic and formative assessment. The initiative was started after finding that those students who couldn’t score good marks are now scoring very high marks conducted online or offline in flipped mode. To assure whether the students actually know the concepts, the teachers have started asking oral questions as part of evaluation and to justify the score obtained by the students in tests (MCQ or descriptive).

## ELECTROSTATICS (Module 1)

1. What is frictional electricity?
2. What is electrostatics?
3. What is static electricity?
4. Name two devices which work on the basis of static electricity.
5. What is the cause of frictional electricity?
6. What is triboelectric series?
7. State the principle of quantisation of charge.
8. State the principle of conservation of charge.
9. Explain additive nature of charge.
10. What is the nature of force between unlike charges and like charges?
11. State Coulomb’s law.
12. What are the limitations of Coulomb’s law?
13. State the principle of superposition of electrostatic force.
14. What do you mean by linear density of charge?
15. What do you mean by surface charge density?
16. How can you prove that there are two kinds of charges?
17. How can you prove that like charges repel and unlike charges attract?
18. What are dielectric and non electric substances?
19. What is the effect of placing a dielectric in between two charges on the force between them?
20. Define relative permittivity or dielectric constant of a medium?
21. What is the value of absolute electric permittivity of free space?
22. What is the unit of relative permittivity (or dielectric constant)?
23. What is the unit of absolute permittivity?
24. Define dielectric constant of a medium in terms of force between two point charges.
25. If the force between two point charges of magnitude q each separated by a distance r is F, then how will the force between the two charges be affected if a third point charge 4q is kept at a distance 2r from either of the charges?

(We are not posting the answers now. Please try to answer in the comment box quoting the question number. Alo ask if you don’t know the answers, quoting the question number.)

## The Ring Launcher Experiment and Eddy Currents

What are eddy currents?

The video focuses upon the demonstration of the concept of Eddy Currents and the application of Lenz Law, using a device called- RING LAUNCHER

Eddy currents are loops of electrical current induced within solid conductors by a changing magnetic field in the conductor according to Faraday’s law of induction. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field.

Lenz’s law. A principle stating that an electric current, induced by a source such as a changing magnetic field, always creates a counterforce opposing the force inducing it. This law explains such phenomena as diamagnetism and the electrical properties of inductors.

Lenz’s Law explains the production of eddy current in a changing magnetic field.

Primarily, eddy currents will be introduced in the material, when an electrically conductive material is placed in the coils magnetic field an electromagnetic induction occurs.

The magnitude of the eddy currents produces a large current since the resistance of the metallic conductor becomes low. They may produce undesirable effects if the large eddy current is allowed to in the core of a choke coil, transformer, etc.

By making use of a laminated core, the eddy currents produced in the core of a transformer are reduced. In the present day, electric brakes are provided on the trains in addition to those vacuum brakes.

## Electromagnetic Induction for Class 12

EMI: Electromagnetic Induction is the phenomenon in which an emf is produced across the ends of a coil whenever the magnetic flux linked with it changes.

Induced EMF

the EMF induced across the ends of a coil due to change in the magnitude of magnetic flux linked with it is called induced emf

Induced Current

If the coil is in a closed circuit, and whenever the magnetic flux linked with it changes, a current flows through it. This current flowing through a coil in a closed circuit due to the change in magnetic flux linked with it is called induced current.

## Kinematics: Equations of uniformly accelerated Motion

Watch the following video to understand Kinematic Equations for uniformly accelerated motion

## Physics Study Materials fr Class XII

You can download here the Physics study materials for class XII CBSE Physics. The material will be useful for revision for AISSCE 2020 and afterwards.