Q. In a nuclear reactor, what is the function of a moderator?

Q. A coil has a self-inductance of $0.05$ henry. Find magnitude of the emf induced in it when the current flowing through it is changing at the rate $100A{s}^{-1}$.

Q. Calculate angular momentum of an electron in the third Bohr orbit of hydrogen atom.

Q. Name the principle on the basis of which optical fibres work.

Q. What is the difference between polarised light and unpolarised light?

Q. Two metals A and B have work functions 4eV and 6eV respectively. Which metal has lower threshold wavelength for photoelectric effect?

Q. Total energy of an electron in the ground state of hydrogen atom is $-13.6eV$. Its total energy, when hydrogen atom is in the first excited state, is:

1. $+13.6eV$
2. $+3.4eV$
3. $-3.4eV$
4. $-54.4eV$

Q. In our Nature, where is the nuclear fusion reaction taking place continuously?

Q. i. State Gauss' law.
ii. In an electric dipole, at which point is the electric potential zero?

Q. For a metallic conductor, what is the relation between current density $\left(j\right)$, conductivity $\left(\sigma \right)$ and electric field Intensity $E$?

Q. Obtain an expression for equivalent capacitance when three capacitors $C_1,C_2$ and $C_3$ are connected in series.

Q. i. Define Curie temperature.
ii. If magnetic susceptibility of a certain magnetic material is $0.0001$, find its relative permeability.

Q. A charged oil drop weighing $1.6\times {10}^{-15}N$ is found to remain suspended in a uniform electric field of intensity $2\times {10}^{3}N{C}^{-1}$. Find the charge on the drop.

Q. State how a moving coil galvanometer can be converted into an ammeter.

Q. Calculate dispersive power of a transparent material with the given:
$n_v=1.56,n_r=1.54,n_y=1.55$

Q. Write the expression for the Lorentz force $F$ in vector form.

Q. A carbon resistor has coloured bands as shown in Figure given below. The resistance of the resistor is:

1. $26\Omega \pm 10\%$
2. $26\Omega \pm 5\%$
3. $260\Omega \pm 5\%$
4. $260\Omega \pm 10\%$

Q. If current through the conductor Y is reversed in direction, will neutral point lie between X and Y, to the left of X or to the right of Y?

Q. In figure given above, find the value of resistance $X$ for which points $A$ and $B$ are at the same potential :

Q. A solenoid L and a resistor R are connected in series to a battery, through a switch. When the switch is put on, current I flowing through it varies with time t as shown in which of the graphs given below:

1. 
   
2. 
   
3. 
   
4. 
   

Q. In the circuit shown in Figure above, $E_1$ and $E_2$ are two cells having emfs 2V and 3V respectively, and negligible internal resistances. Applying Kirchhoff's laws of electrical networks, find the values of currents $I_1$ and $I_2$.

Q. Two point charges $Q_1=400\mu C$ and $Q_2=100\mu C$ are kept fixed, 60 cm apart in vacuum. Find intensity of the electric field at midpoint of the line joining $Q_1$ and $Q_2$.

Q. Draw a labelled circuit diagram of a potentiometer to measure internal resistance of a cell. Write the working formula. (Derivation not required).

Q. What is meant by short-sightedness?

Q. In given Figure, a charge Q is fixed. Another charge q is moved along a circular arc MN of radius r around it, from the point M to the point N such that the length of the arc $MN=l$. The work done in this process is :

1. Zero
2. $\frac{1}{4\pi {ϵ}_0}.\frac{Qq}{r^2}l$
3. $\frac{Qq}{2{ϵ}_0{r}^2}l$
4. $\frac{Qq}{2\pi {ϵ}_0{r}^2}$

Q. Two infinitely long current carrying conductors X and Y are kept parallel to each other, 24 cm apart in vacuum. They carry currents of 5A and 7A respectively, in the same direction, as shown in Figure above. Find the position of a neutral point, i.e. a point where resultant magnetic flux density is zero.
(Ignore earth's magnetic field).

Q. A metallic wire has a resistance of $3.0\Omega$ at $0^{o}C$ and $4.8\Omega$ at ${150}^{o}C$. Find the temperature coefficient of resistance of its material.

Q. Two thin lenses having optical powers of $-10D$ and $+6D$ are placed in contact with each other. The focal length of the combination is:

1. $+0.25cm$
2. $-0.25cm$
3. $+0.25m$
4. $-0.25m$

Q. To which regions of the electromagnetic spectrum do the following wavelengths belong :
(a) $250nm$
(b) $1500nm$

Q. What is the use of a Zener diode?