Posts Tagged ‘expression’

CLASS XII PHYSICS SAMPLE PAPER FOR AISSCE 2012

CLASS XII – SAMPLE PAPER

PHYSICS

Time allowed : 3 hours

Max. Marks : 70

General Instructions:

1. All questions are compulsory
2. There are 30 questions in total. Questions 1 to 8 carry one mark each, 9 to 18 carry two marks each, 19 to 27 carry 3 marks each and 28 to 30 carry 5 marks each.
3. There is no overall choice, but internal choices are provided. You have to attempt only one choice in full.
4. Use of calculator is not permitted.
5. You may use the logarithm table, if required.

1. Express dielectric constant in terms of capacitance.

2. What is magnetic susceptibility?

3. Define electromagnetic induction. Read more…

Height of Antenna and range of transmission

A TV Tower has a height h. Derive expression for the maximum distance upto which signals can be received on earth.

Height of Antenna and Range of Transmission

Electrostatics : A Practice Test Paper – 1

Time: 45 min

Max. Marks: 25

1. How does the force between two point charges change, if the dielectric constant of the medium in which they are kept, increases? [1]
2. Name the experiment which established the quantum nature of electric charge. [1]
3. Ordinary rubber is an insulator, but the special tyres of aircrafts are made slightly conducting. Why is this necessary? [1]
4. Draw electric field lines around an electric dipole. [1]
5. What would be the work done if a point charge +q is taken from  a point A to B on the circumference of a circle with another point charge +q at the centre? [1]
6. Obtain an expression for the potential energy of two charges q1 and q2 separated by distance r in a electric field E. [2]
7. Define electric field intensity. What is its SI unit? What is the relation between electric field and force on the charge? [2]
8. Obtain an expression for the electric potential at a point due to an electric dipole. [3]
9. Sketch equipotential surfaces for (i) a positive point charge (ii) Two equal positive point charges separated by a small distance (iii) a uniform electric field. [3]
10. (a) State Gauss Law (b) Using it derive an expression for the electric field intensity at a point near a thin infinite plain sheet of charge. (c) A point charge of 2 microcoulomb is at the centre of a cubic Gaussian surface 9cm edge. What is the net electric flux through all the surfaces of the cube? [5]
11. (a) Define electric dipole moment. (b) Derive expression for electric field intensity of a dipole at a point on its axial line. (c) Two charges +10μ C and – 10 μ C are placed 5 mm apart. Determine the electric field at a point P 15 cm away from its centre O on a line passing through O and normal axis of the dipole. [5]

Derive an expression for current in terms of drift velocity. (Derive I = nAev)

(This is being posted as per request from students)

Consider a conductor of length l and area of cross section A. Let the number of free electrons per unit volume be n. When a pd V is applied, let the drift velocity of electrons be v.

The total no. of free electrons in the piece of conductor = nAl (no. of free electrons per unit volume x volume)

Total charge due to free electrons; q  = nAle

The time taken by this charge to completely traverse the conductor, t =l/v

Therefore, the current in the conductor, I=q/t = nAle/(l/v) = nAev

i.e; I=nAev

Class XII Physics SOME QUESTIONS FROM CBSE 2004 Board Question Paper

Physics 2004 Set 1

1. Why is shortwave band used for long distance radio broadcast?
2. Two metals A and B have work functions 2 eV and 5 eV respectively. Which metal has lower threshold wavelength?
3. Draw the voltage-current characteristic of a zener diode.
4. A solenoid with an iron core and a bulb is connected to a d.c. source. How does the brightness of the bulb change when the iron core is removed from the solenoid?
5. Peak value of e.m.f of an a.c. source is E0. What is its r.m.s value?
6. An electric dipole of length 4 cm, when placed with its axis making an angle of 60° with a uniform electric field, experiences a torque of Nm. Calculate the (i) magnitude of the electric field (ii) potential energy of the dipole, if the dipole has charges of ± 8 nC.
7. Explain how the resistivity of a conductor depends upon (i) number density ‘n’ of free electrons, and (ii) relaxation time ‘λ’.
8. Two long parallel straight wires X and Y separated by a distance of 5 cm in air carry currents of 10 A and 5 A respectively in opposite directions. Calculate the magnitude and direction of the force on a 20 cm length of the wire Y.

Read more…

Revision Test Series for Class XI – Oscillations

Download as PDF oscillations

PHYSICS TEST PAPER (OSCILLATIONS)

Time : 1 ½hr M. Marks: 40

• Q.Nos 1 to 5 carries 1 mark each
• QNos 6 to 10 carry 2 marks each
• QNos 11 to 15 carry 3 marks each
• QNos 16 – 17 carry 5 marks each

1.      What is periodic motion?

2.      How will the time period of a simple pendulum change if its length is doubled?

3.      Two identical springs of force constant k each are connected in series. What will be the equivalent spring constant?

4.      What is the time period of a simple pendulum in a satellite orbiting around the earth? Read more…

SET OF MUST PRACTICE QUESTIONS FOR CBSE PHYSICS CLASS XII (AISSCE PHYSICS 2011)

Hello Dear Students, If you were searching for a set of questions which you cannot afford to leave while preparing for AISSCE 2011 Physics Exam, Here it is. Please practice them carefully. If you have any doubt in answering any of these questions, please feel free to ask at www.askphysics.com The content is being updated by adding more questions daily. So please come back soon for more

ELECTROSTATICS

1. State Coulomb’s law and express it in vector form
2. Derive an expression for the electric field due to a dipole at a point on its
   1. axial position and
   2. on the equatorial position.
3. State Gauss theorem of electrostatics and use it to find the electric field at a point due to
   

   1. A point charge
   2. A line of charge
   3. A plane sheet of charge
   4. A sphere of charge

4. Derive Coulomb’s law from Gauss theorem
5. Derive an expression for the torques on a dipole in a uniform electric field
6. Derive an expression for the work done in rotating a dipole in a uniform electric field
7. Derive an expression for t6he potential energy of a dipole in a unifor electric field
8. Derive an expression for the potential energy of a system of point charges
9. Describe the principle of a parallel plate capacitor
10. Derive an expression for the capacitance of a parallel plate capacitor.
11. Derive an expression for the effective capacitance when capacitors are connected in (a) parallel (b) series
12. Derive an expression for the energy stored in a parallel plate capacitor
13. Derive an expression for the electric potential due to (a) a point charge (b) a system of point charges
14. Describe the principle construction and working of Van de Graff generator

CURRENT ELECTRICITY

1. State Ohm’s law
2. Define drift velocity and derive an expression for it.
3. Derive the relation I = nAev
4. Deduce Ohm’s law
5. Explain why the resistance of a conductor increases with increase in temperature.
6. Derive expression for the effective resistance when three resistors are connected in (a) series (b) parallel
7. State Kirchhoff laws
8. What is a Wheatstone’s bridge? State its principle and deduce it using Kirchhoff laws.
9. Explain how a metre bridge is used to determine the resistance of a given wire.
10. State and explain the Principle of a potentiometer and describe the experiment to determine the internal resistance of a primary cell using potentiometer.
11. Describe how a potentiometer is used to compare the emfs of two primary cells.

To be updated soon

MAGNETIC EFFECTS OF CURRENT

1. State Biot Savart law and apply it to determine the strength of magnetic field at a point on the axis of a circular coil carrying current
2. State Ampere’s circuital law and apply it to find the magnetic field inside a solenoid and a toroid.
3. Describe the principle construction and working of a cyclotron. Why a cyclotron cannot be used to accelerate electrons
4. Derive an expression for cyclotron frequency
5. Explain the principle construction and working of a moving coil galvanometer.
6. Define the terms figure of merit and sensitivity of a galvanometer.
7. Describe how will you convert a galvanometer into (a) ammeter (b) voltmeter

To be updated soon

ELECTROMAGNETIC INDUCTION AND AC

To be uploaded soon

ELECTROMAGNETIC WAVES

1. Describe Hertz experiment to produce em waves
2. Write the properties of em waves
3. What is em spectrum? Write any 5 constituents of em spectrum in the order of increasing wavelength. Write two uses of each
4. Write Maxwell’s equations.
5. Discuss the inconsistency of Ampere’s circuital law and how it is removed in Ampere – Maxwell law.
6. What is displacement current?
7. Explain how em waves are produced?
8. Describe the transverse nature of em waves. (Show that em waves are transverse in nature)

To be uploaded soon

OPTICS

To be uploaded soon

DUAL NATURE OF MATTER AND RADIATIONS

To be uploaded soon

ATOMS AND NUCLEI

To be uploaded soon

ELECTRONIC DEVICES

To be uploaded soon

COMMUNICATION SYSTEMS

One mark questions

1. What is the meant by the term attenuation ?

2. Why ground wave transmission is restricted to 1500 kHz?

3. Define critical frequency in sky wave propagation.

4. What type of modulation is required in TV transmission?

5. Why AM radio reception is affected by electrical disturbances while FM radio reception is not?

6. What should be the length of a dipole antenna for a carrier wave of frequency 3 x 108 Hz

7. Draw a block diagram showing the basic communication system.

8. What is the range of frequencies used for FM radio transmission?

Two marks Questions

1. Distinguish analog and digital transmission

2. Write the functions of transducer and repeater in Communication systems. 3. Distinguish amplitude modulation and frequency modulation.

4. Draw a block diagram showing a simple amplitude modulator

5. Explain how a message signal is extracted from Amplitude Modulated signal.

6. Distinguish Sky wave propagation and Space wave propagation.

7. Name the different layers of earth’s atmosphere.

8. Mention two ways in which the range of transmission can be increased.

9. Explain the term modulation index and describe its significance.

10. List four devices used for communication each of which differ from other in the mode of communication.

Three marks questions

1. Explain the need for modulation

2. Derive an expression for the range of transmission from an antenna of height h.

3. Describe the demodulation of AM wave using waveforms and circuit diagrams.