Q. Two identical cells, each of emf E, having negligible internal resistance are connected in parallel with each other across an external resistance R. what is the current through this resistance?

Q. Two charges of magnitudes $-2Q$ and $+Q$ are located at points $(a,0)$ and $(4a,0)$ respectively. What is the electric flux due to these charges through a sphere of radius ${}^{\prime }3a^{\prime }$ with its centre at the origin?

Q. Explain the term 'drift velocity' of electrons in a conductor. Hence obtain the expression for the current through a conductor in terms of 'drift velocity'.

Q. (a) Using Biot-Savart's law, derive the expression for the magnetic field in the vector form at a point on the axis of a circular current loop
(b) What does a toroid consist of? Find out the expression for the magnetic field inside a toroid for N turns of the coil having the average radius r and carrying a current I. Show that the magnetic field in the open space inside and exterior to the toroid is zero.

Q. How does the mutual inductance of a pair coils change when
$\left(i\right)$ distance between the coils is increased and
$\left(ii\right)$ number of turns in the coils is increased?

Q. In the circuit shown in the figure identify the equivalent gate of the circuit and make its truth table .

Q. One day Chetan's mother developed a severe stomach ache all of a sudden. She was rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately asked her class teacher and arranged the money and rushed to the hospital. On realizing that Chetan belonged to a below average income group family even the doctor offered concession for the test fee. The test was conducted successfully .
Answer the following questions based on the above information;
(a) Which principle in optics is made use of in endoscopy.?
(b) Briefly explain the values reflected in the action taken by the teacher.
(c) In what way do you appreciate the response of the doctor on the given situation?

Q. Write Einstein's photoelectric equations and point out any two characteristic properties of photons on which this equations is based.
Briefly explain the three observed features which can be explained by this caution.

Q. Using Bohr's postulates derive the expression for the frequency of radiation submitted when electron in hydrogen atom undergoes transition from higher energy state (quantum number $n_i$) to the lower state, $\left(n_f\right)$
when electron in hydrogen atom jumps from energy state $n_i=4to{n}_f=3,2,1$. Identify the special series to which the emission lines holding belong.

Q. The motion of copper plate is damped when it is allowed to oscillate between the two poles of a magnet. What is the cause of this damping?

Q. The graph shown in the figure represents a plot of current versus voltage for given semi-conductor. Identify the region. if any, over which the semi-conductor has a negative resistance.

Q. (a) For a given a.c., $i=i_{m}sin\omega t$, show that the average power dissipated in a resistor R over a complete cycle is $\frac{1}{2}{i}_m^{2}R$
(b) A light bulb is rated at 100 W for a 220 V a.c. supply
Calculate the resistance of the bulb

Q. Draw a typical output characteristics of an n-p-n transistor in CE configuration. Show how these characteristics can be used to determined output resistance .

Q. A rectangular conductor $LMNO$ is placed in a uniform magnetic field of $0.5T$. The field is directed perpendicular to the plane of the conductor. When the arm $MN$ of length of $20cm$ is moved towards left with a velocity of $10m{s}^{-1}$ calculate the emf induced in the arm. Given the resistance of the arm to be $5\Omega$ (assuming that other arms are of negligible resistance) find the value of the current in the arm.

Q. A wire AB is carrying a steady current 12 A and is lying on the table. Another wire CD carrying 5 A is held directly above AB at a height of 1 mm. Find the mass per unit length of the wire CD so that it remains suspended at its position when left free. Give the directions of the current flowing in CD with respect to that in AB [Take the value of $g=10m{s}^{-2}$]

Q. A slab of material of dielectric constant K has the same area as that of the plates of a parallel plate capacitor but has the thickness d/2, where d is the separation between the plates. Find out the expression for its capacitance when the slab is inserted between the plates of the capacitor .

Q. What are permanent magnets? Give one example.

Q. A convex lens of focal length $f_1$ is kept in contact with a concave lens of focal length $f_2$. Find the focal length of the combination.

Q. A capacitor made of two parallel places each of plate area A and separations d, being charged by an external ac source. How the displacement current inside the capacitor is same as the current charging the capacitor

Q. Write the expression for the Broglie wavelength associated with a charged particle having charge 'q' and mass 'm', when it is accelerated by a potential V.

Q. Define the current sensitivity of a galvanometer. Write S.I unit
Figure shows two circuits each having a galvanometer and a battery of 3V
When the galvanometer in each arrangement do not show any deflection obtain the ratio $R_1/R_2$

Q. Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Names the radiations and write the range of their frequency

Q. Define the activity of a given radioactive substance. write its S.I units

Q. (a) What is linearly polarized light. Describe briefly using a diagram how sunlight is polarised.
(b) Unpolarised light is incident on a Polaroid. How would the intensity of transmitted light change when the Polaroid is rotated?

Q. A parallel beam of light of 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Calculate the width of the slit.

Q. Name the type of waves which are used for line of sight (LOS) communications. What is the range of their frequencies?
A transmitting antenna at the top of a tower has a height of 20 m and the height of the receiving antenna is 45 m. Calculate the maximum distance between them for satisfactory communication in LOS mode.(Radius of the Earth $=6.4\times {10}^{6}m$)

Q. (a) Define electric dipole moment. Is it a scalar or a vector?
Derive the expression for the electric field of a dipole at a point on the equatorial plane of the dipole.
(b) Draw the equipotential surface due to an electric dipole. Locate the points where the potential due to the dipole is zero.

Q. Draw a labeled ray diagram of a refracting telescope. Define its magnifying power and write the expression for it.
Write two important limitation of a refracting telescope over a reflecting type telescope

Q. In the block diagram of a simple modulator for obtaining an AM signal shown in the figure, identify the boxes A and B.
Write their functions,

Q. Draw V-I characteristics of a p-n junction diode. Answer the following questions, giving reasons:
(i) Why is the current under reverse bias almost independent
of the applied upto a critical voltage?
(ii) Why does the reverse current show a sudden increase at the critical voltage?
Name any semiconductor device which operates under the reverse bias in the breakdown regions