Q. Prove that for A.C. circuit:
$P_{av}=V_{r.m.s.}\times I_{r.m.s.}cos\varphi$

Q. Zener diode is used as ......................

Q. The Magnetic effect of current was discovered by:

1. John Ambrose Fleming
2. André-Marie Ampère
   
3. Michael Faraday
4. Hans Christian Oersted

Q. Write the meaning of laser and two uses.

Q. State Biot-Savart's law. Define unit of current.

Q. The conductivity of superconductor is

1. Very less
2. Infinity
3. Zero
4. Very large

Q. Write the causes of energy loss and ways to reduce them in transformer (any four).

Q. Meter bridge works on the principle of

Q. Define the following:
Threshold frequency and work function.

Q. How can a galvanometer be converted into voltmeter?

Q. Which waves are used as signal through fog and why?

Q. The mass of a moving particle is m and velocity is v, then write the formula for de-Broglie wavelength $\lambda$.

Q. The angle between electric lines of force and equipotential surface is :

1. 180${}^o$
2. 0${}^o$
3. 45${}^o$
4. 90${}^o$

Q. What is greenhouse effect? Explain.

Q. Select the appropriate option from column 'B' for each statement of column 'A' and match the correct pair

Q. Prove that
$I^2=H^2+V^2$ and $tanq=\frac{V}{H}$; where for terrestrial magnetism $\theta$ angle of dip, H horizontal component and vertical component.

Q. Write any two differences between regular and irregular (diffused) reflection.

Q. Establish relation $d=\sqrt{2hR}$ between height h of the TV antenna and distance d upto which TV signal can be transmitted, where R = Radius of earth.

Q. Eddy currents are used in

1. electrolysis
2. making a galvanometer dead beat
3. electroplating
4. to increase the sensitivity of galvanometer

Q. The formula for the velocity of electromagnetic waves in vacuum is given by

1. $c=\sqrt{\frac{{\epsilon }_0}{{\mu }_0}}$
2. $c=\frac{1}{\sqrt{{\mu }_0{\epsilon }_0}}$
3. $c=\sqrt{\frac{{\mu }_0}{{\epsilon }_0}}$
4. $c=\sqrt{{\mu }_0\epsilon }$

Q. Describe the astronomical telescope on the basis of the following points:
(i) Labelled Ray diagram.
(ii) Derivation of formula for magnifying power, when final image is formed at the least distance of distinct vision.

Q. Write down four differences between interference and diffraction.

Q. Write any two advantages of optical communication.

Q. Write the use of Fax Machine.

Q. The work function of a metal is 0.1 eV. Calculate the threshold frequency for photo-electric emission.

Q. In a parallel plate capacitor with increase in distance between the plates, its capacity ................

Q. For healthy eye least distance of distinct vision is ..................

Q. How are N-type of semiconductors prepared?

Q. An air bubble inside water behaves like a ................... lens.

Q. When an object is kept in between optical centre and focus in front of convex lens, draw ray-diagram of image formation.