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#### Important 3 Mark Creative Questions (New Syllabus) 2020

12th Standard EM

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Physics

Time : 01:00:00 Hrs
Total Marks : 48

Part A

16 x 3 = 48
1. Derive the expressions for the potential energy of a system of point charges.

2. Explain the Lightning arrester or lightning conductor.

3. Derive a relation between internal resisance and emf of a cell

4. Tabulate the difference between Coulomb's law and Biot-Savort's law.

5. In a certain region of space, electric field $\vec { E }$ and magnetic field $\vec { B }$ are perpendicular to each other. An electron enters in the region perpendicular to the direction of both $\vec { B }$ & $\vec { E }$ and moves undeflected. Find the velocity of electron.

6. Can a galvanometer be used for measuring the current? Explain.

7. How does the capacitive reactance depend on frequency? & What is the reactance of a capacitor at hertz to the study at?

8. The charge on a parallel plate capacitor varies as q=qo cos 2$\pi \gamma$t. The plates are very large and close together. (area-A. separation - d) find the displacement current through the capacitor?

9. Define refractive index of a medium.

10. What is thin lens?

11. Write three characterists features in photoelectric effect which cannot be explained on the basis of wave theory of light, but can be explained only using Einstein's equation.

12. (i) Draw a graph showing variation of photoelectric current (I) with anode potential (V) for different intensities of incident radiation. Name the characteristic of the incident radiation that is kept constant in this experiment.
(ii) If the potential difference used to accelerate electrons is doubled, by what factor does the de-Broglie wavelength associated with the electrons change?

13. Write the properties of neutrino?

14. What is electronics?

15. Why space wave propagation is limited upto small distance over earth's surface?

16. Write the aim of artificial intelligence in robots.