2011-2012 March

When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction?

Chapter: [2.01] Current Electricity

The horizontal component of the earth’s magnetic field at a place is B and angle of dip is 60°. What is the value of vertical component of earth’s magnetic field at equator?

Chapter: [3.01] Magnetism and Matter

Show on a graph, the variation of resistivity with temperature for a typical semiconductor.

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

Why should electrostatic field be zero inside a conductor?

Chapter: [1.01] Electrostatic Potential and Capacitance

Name of physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.

Chapter: [5.01] Electromagnetic Waves

Under what condition does a biconvex lens of glass having a certain refractive index act as a plane glass sheet when immersed in a liquid?

Chapter: [6.01] Ray Optics and Optical Instruments

Predict the directions of induced currents in metal rings 1 and 2 lying in the same plane where current I in the wire is increasing steadily.

Chapter: [4.02] Electromagnetic Induction

State de Broglie hypothesis

Chapter: [7.01] Dual Nature of Radiation and Matter

A ray of light, incident on an equilateral prism `(μ_g = sqrt3)`moves parallel to the base line of the prism inside it. Find the angle of incidence for this ray.

Chapter: [6.01] Ray Optics and Optical Instruments

Distinguish between ‘Analog and Digital signals’.

Chapter: [10.01] Communication Systems

Mention the function of any two of the following used

(i) Transducer

(ii) Repeater

(iii) Transmitter

(iv) Bandpass Filter

Chapter: [10.01] Communication Systems

A cell of emf E and internal resistance r is connected to two external resistance R_{1} and R_{2} and a perfect ammeter. The current in the circuit is measured in four different situations:

(i) without any external resistance in the circuit

(ii) with resistance R_{1} only

(iii) with R_{1} and R_{2} in series combination

(iv) with R_{1} and R_{2} in parallel combination

The currents measured in the four cases are 0.42 A, 1.05 A, 1.4 A and 4.2 A, but not necessarily in the order. Identify the currents corresponding to the four cases mentioned above.

Chapter: [2.01] Current Electricity

The susceptibility of a magnetic material is − 2.6 × 10^{−5}. Identify the type of magnetic material and state its two properties.

Chapter: [3.01] Magnetism and Matter

Two identical circular wires P and Q each of radius R and carrying current ‘I’ are kept in perpendicular planes such that they have a common centre as shown in the figure. Find the magnitude and direction of the net magnetic field at the common centre of the two coils.

Chapter: [3.02] Moving Charges and Magnetism

When an ideal capacitor is charged by a dc battery, no current flows. However, when an ac source is used, the current flows continuously. How does one explain this, based on the concept of displacement current?

Chapter: [5.01] Electromagnetic Waves

Draw a plot showing the variation of (i) electric field (E) and (ii) electric potential (V) with distance r due to a point charge Q.

Chapter: [1.01] Electrostatic Potential and Capacitance

Define self-inductance of a coil. Show that magnetic energy required to build up the current I in a coil of self inductance L is given by `1/2 LI^2`

Chapter: [4.02] Electromagnetic Induction

The current in the forward bias is known to be more (~mA) than the current in the reverse bias (~*μ*A). What is the reason, then, to operate the photodiode in reverse bias?

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

A metallic rod of ‘L’ length is rotated with angular frequency of ‘ω’ with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius L, about an axis passing through the centre and perpendicular to the plane of the ring. A constant and uniform magnetic field B parallel to the axis is presents everywhere. Deduce the expression for the emf between the centre and the metallic ring.

Chapter: [4.02] Electromagnetic Induction

The figure shows a series LCR circuit with L = 10.0 H, C = 40 *μ*F, R = 60 Ω connected to a variable frequency 240 V source, calculate

(i) the angular frequency of the source which drives the circuit at resonance,

(ii) the current at the resonating frequency,

(iii) the rms potential drop across the inductor at resonance.

Chapter: [4.01] Alternating Current

A rectangular loop of wire of size 4 cm × 10 cm carries a steady current of 2 A. A straight long wire carrying 5 A current is kept near the loop as shown. If the loop and the wire are coplanar, find

(i) the torque acting on the loop and

(ii) the magnitude and direction of the force on the loop due to the current carrying wire.

Chapter: [3.02] Moving Charges and Magnetism

Using Bohr’s second postulate of quantization of orbital angular momentum show that the circumference of the electron in the *n*^{th} orbital state in hydrogen atom is *n* times the de Broglie wavelength associated with it.

Chapter: [8.02] Atoms

The electron in hydrogen atom is initially in the third excited state. What is the maximum number of spectral lines which can be emitted when it finally moves to the ground state?

Chapter: [8.02] Atoms

In the figure a long uniform potentiometer wire AB is having a constant potential gradient along its length. The null points for the two primary cells of emfs ε_{1} and ε_{2} connected in the manner shown are obtained at a distance of 120 cm and 300 cm from the end A. Find (i) ε_{1}/ ε_{2} and (ii) position of null point for the cell ε_{1}.

How is the sensitivity of a potentiometer increased?

Chapter: [2.01] Current Electricity

Using Kirchhoff’s rules determine the value of unknown resistance R in the circuit so that no current flows through 4 Ω resistance. Also find the potential difference between A and D.

Chapter: [2.01] Current Electricity

What characteristic property of nuclear force explains the constancy of binding energy per nucleon (BE/A) in the range of mass number ‘A’ lying 30 < A < 170?

Chapter: [8.01] Nuclei

Show that the density of nucleus over a wide range of nuclei is constant-independent of mass number A.

Chapter: [8.01] Nuclei

Write any two factors which justify the need for modulating a signal ?

Chapter: [10.01] Communication Systems

Draw a diagram showing an amplitude modulated wave by superposing a modulating signal over a sinusoidal carrier wave.

Chapter: [10.01] Communication Systems

Write Einstein’s photoelectric equation?

Chapter: [7.01] Dual Nature of Radiation and Matter

State clearly how photoelectric equation is obtained using the photon pictu.re of electromagnetic radiation.

Chapter: [7.01] Dual Nature of Radiation and Matter

Write the three salient features observed in photoelectric effect which can be explained using this equation.

Chapter: [7.01] Dual Nature of Radiation and Matter

Why are coherent sources necessary to produce a sustained interference pattern?

Chapter: [6.02] Wave Optics

In Young’s double slit experiment using monochromatic light of wavelength *λ*, the intensity of light at a point on the screen where path difference is *λ*, is K units. Find out the intensity of light at a point where path difference is *λ*/3.

Chapter: [6.02] Wave Optics

Use Huygens’s principle to explain the formation of diffraction pattern due to a single slit illuminated by a monochromatic source of light.

Chapter: [6.02] Wave Optics

When the width of the slit is made double the original width, how would this affect the size and intensity of the central diffraction band?

Chapter: [6.02] Wave Optics

Explain the principle of a device that can build up high voltages of the order of a few million volts.

Chapter: [1.01] Electrostatic Potential and Capacitance

Draw a schematic diagram and explain the working of Van de Graff generator device.

Chapter: [1.01] Electrostatic Potential and Capacitance

Is there any restriction on the upper limit of the high voltage set up in Van de Graff generator machine? Explain.

Chapter: [1.01] Electrostatic Potential and Capacitance

Define Electric Flux. Write its SI unit.

Chapter: [1.02] Electric Charges and Fields

Using Gauss’s law, prove that the electric field at a point due to a uniformly charged infinite plane sheet is independent of the distance from it.

Chapter: [1.02] Electric Charges and Fields

How is the field directed if (i) the sheet is positively charged, (ii) negatively charged?

Chapter: [1.02] Electric Charges and Fields

Define magnifying power of a telescope. Write its expression.

Chapter: [6.01] Ray Optics and Optical Instruments

A small telescope has an objective lens of focal length 150 cm and an eye piece of focal length 5 cm. If this telescope is used to view a 100 m high tower 3 km away, find the height of the final image when it is formed 25 cm away from the eye piece.

Chapter: [6.01] Ray Optics and Optical Instruments

How is the working of a telescope different from that of a microscope?

Chapter: [6.01] Ray Optics and Optical Instruments

The focal lengths of the objective and eyepiece of a microscope are 1.25 cm and 5 cm respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal adjustment.

Chapter: [6.01] Ray Optics and Optical Instruments

Draw a simple circuit of a CE transistor amplifier. Explain its working ?

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

Show that the voltage gain, A_{V}, of the amplifier is given by `A_v = (beta_(ac) R_1)/r_i`where β_{ac} is the current gain, R_{L} is the load resistance and r_{i} is the input resistance of the transistor. What is the significance of the negative sign in the expression for the voltage gain?

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

Draw the circuit diagram of a full wave rectifier using p-n junction diode.

Explain its working and show the output, input waveforms.

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

Show the output waveforms (Y) for the following inputs A and B of (i) OR gate (ii) NAND gate ?

Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits

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