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Showing posts with label class12-Physics. Show all posts
Showing posts with label class12-Physics. Show all posts

## Cathode Rays and Its Properties

 Image Credits: Wikipedia, Author: Theresa Knott

Q1: What are Cathode Rays?

Answer: are streams of electrons observed in vacuum tubes. These rays were discoevered by a German physicist Johann Wilhelm Hittorf, and were named in 1876 by E. Goldstein, or cathode rays. In 1897, British physicist J. J. Thomson experimented and showed that cathode rays were composed of negatively charged particles, called electrons. Cathode rays are also called as electrons beam.

When a potential difference of 10 to 15 kV is applied across the two electrodes of a discharge tube and pressure is reduced to 0.01mm of mercury, the rays known as cathode rays are emitted from the cathode. These rays are independent of the nature of the gas in the discharge tube and their direction of propagation is not affected by the position of the anode.

Q2: What are the properties of Cathode Rays?

## Wave Optics

(Important Theory Questions)

Q1. Define wave front. State Huygens principle and verify Snell’s law.

Q2. State Huygens principle and prove the laws of reflection on the basis of wave theory.

Q3. What do you mean by interference of light? Explain in brief the Young’s double slit experiment.

Q4. What are the coherent sources? Write the conditions for the sustained interference pattern. Also draw the intensity v/s path difference curve.

## Ray Optics

(Important Theory Questions)

1. Derive mirror formula for a concave mirror and convex mirror.

2. Derive an expression for lateral shift and normal shift. On what factors these depend.

3. Define TIR and write the conditions for TIR. Derive a relation between critical angle and the refractive index of the medium. Also explain the working of isosceles prism and optical fiber.

4. Derive the following relation for a real image formed by a convex refracting surface when the object is placed in rarer medium. Also write the assumptions and sign convention used.

μ₂ / v - μ₁/u = (μ₂ - μ₁) / R

## Electromagnetic Waves

(Important Theory Questions)

1. Explain the inadequacy of Ampere's circuital law

2. Describe Hertz experiment to demonstrate the production of electromagnetic waves

3. Write the properties of electromagnetic waves.

4. Write any five electromagnetic waves in the order of decreasing frequency and write any two properties and uses of each

5. Deduce an expression for velocity of em waves in vacuum.

6. Establish the transverse nature of electromagnetic waves.

7. Compare the properties of electromagnetic waves and mechanical waves.

## Alternative Current

(Important Theory Questions)

1. Describe the principle construction and working of an AC generator. Draw neat labeled diagram

2. Define mean value of AC(over a half cycle) and derive an expression for it.

3. Define RMS value of AC and derive an expression for it. ()

4. Show that the average value of AC over a complete cycle is zero.

5. Show that the current and voltage are in phase in an ac circuit containing resistance only.

## Electromagnetic Induction (EMI)

(Theoretical Questions Assignment)

1. State and Explain Faraday's laws of electromagnetic induction.()

2. State Lenz' Law and show that it is in accordance with the law of conservation of energy.

3. Use Lenz' law to find the direction of induced emf in a coil when
(a) a north pole is brought towards the coil
(b) north pole taken away from the coil
(c) A south pole isbrought towards the coil and
(d) a south pole is taken away from the coil,
Draw illustrations in each case.

## Magnetic Effect of Current

(Theoretical Questions)

1. State Biot- Savart law and apply it to find the magnetic field due to a circular loop carrying current at a point (a) at its centre (b) on the axis

2. State Ampere's circuital law and apply it to find the magnetic field (a) inside a current carrying solenoid (b) inside a current carrying toroid.

3. Apply Ampere's circuital law to determine the magnetic field at a point due to a long straight current carrying conductor.

4. Derive an expression for the force on a current carrying conductor in a uniform magnetic field

## Saturday 5 May 2018

### CBSE Class 12 - Physics - Current Electricity - Important Theory Questions (#cbsenotes)(#eduvictors)

Current Electricity
Important Theory Questions

1. Define drift velocity and derive an expression for it.

2. Derive the expression I=nAevd

3. Deduce Ohm's law from elementary ideas and hence write an expression for resistance and resistivity.

4. Derive an expression for conductivity in terms of mobility

## Electrostatics - Important Theory Questions

1. Derive an expression for the electric field at a point on the axial position of an electric dipole.

2. Derive an expression for the electric field at a point on the equatorial position of an electric dipole.

3. Describe the Principle, construction and working of Van de Graff generator.

4. Derive an expression for the energy stored in a capacitor. Show that whenever two conductors share charges by bringing them into electrical contact, there is a loss of energy.

5. Derive an expression for the effective capacitance when capacitors are connected in
(a) series and
(b) parallel

6. Explain the principle of a capacitor and derive an expression for the capacitance of a parallel plate capacitor.

## DISCOVERIES IN ATOMIC STRUCTURE

1. Dalton(1803) : Proposed Atomic Theory

2. Julius Plucker (1859) : First discoverer of cathode rays

3. Goldstein(1886) : Discovered anode rays and proton

4. Sir.J.J.Thomson(1897) : Discovered electron and determined charge/mass(e/m) ratio for electron

5. Rutherford(1891) : Discovered nucleus and proposed atomic model

## CHAPTER 9 - ELECTRONIC DEVICES - REVISION ASSIGNMENT

1 MARK QUESTIONS

1.  In a semiconductor which of the following carries can contribute to the current?
(a) Electrons
(b) Holes
(c) Both
(d) None

2. A semiconductor diode has ______
(a) One PN junction
(b) Two PN junctions
(c) Three PN junctions
(d) Four PN junctions

3. If the arrow of diode symbol is positive with respect to bar, then the diode is ______ biased

4.  The DC resistance of a diode is _______ its AC resistance.

5. If the temperature of the diode increases,then leakage current ________.

## Light - Reflection From Mirrors (Worksheet)

1. We get a diminished image with a concave mirror when the object is placed ____.

2. The drivers mirror used in automobiles is ____.

3. The distance of focus F from the pole P is termed as the ..................... of the mirror.

4. Mirror formula is ____.

## CBSE Class 12 - Physics Sample Question Paper (2014-15)

Sample Question Paper with Answers and Marking Scheme.

## RAY OPTICS AND OPTICAL INSTRUMENTS

CBSE CLASS 12 - PHYSICS

Q1: What is the focal length and power of a plane glass plate?

Answer: Focal length of plane glass is infinite and its power = 0.

Q2: What is the mathematical relation between object distance (p) and image distance (i) in a plane mirror?

Q3: An object is placed at the focus of  concave lens. Where will its image be formed?

Answer: The real image will be formed at infinity.

Q4: If the speed of light were the same in all media, would refraction still occur when light passes from one medium to another?

Answer: No change in speed of light causes bending of light rays in refraction.

## Physics -Syllabus (2017-18)

### CBSE Class 12 Physics

Here presents the prescribed syllabus for Class 12 Physics for the curriculum 2017-18.

## Electrostatic Potential and Capacitance

CBSE Class 12 - Physics
(Short Q and A)

Q1: Define Electrostatic Potential.

Answer: The electrostatic potential at a point is defined as amount of work done per unit positive test charge in moving the test charge from infinity to that point against the electrostatic force due to the electric field.
Q4: Is electric potential a scalar quantity or vector quantity?

Q2: Name the physical quantity whose SI unit is Joule coulomb⁻ⁱ?

Q3: Does the electric potential increase or decrease along the electric line of force?

Answer: It decreases along the electric line of force.

Q4: Is electric potential a scalar quantity or vector quantity?

## Wednesday 8 February 2017

### CBSE Class 12 - Marking Scheme of Physics Sample Question Paper (2016-17) (#cbsePapers)

CBSE Class 12  - Marking Scheme of Physics Sample Question Paper (2016-17)

See Class 12 Physics Sample Question Paper (2016-17)

## Monday 6 February 2017

### CBSE Class 12 - Physics Sample Question Paper (2016-17) (#cbsepapers)

CBSE Class 12  - Physics Sample Question Paper (2016-17)

See Class 12 Physics Marking Scheme SQP (2016-17)

## Wednesday 18 May 2016

### Class 12 - Physics - Chapter 4: Moving Charges and Magnetism (VSQA)

Moving Charges and Magnetism

### Very Short Q & A

Q1: Define Magnetic Field.

Answer: The space around a magnet within which its effect is experienced is called Magnetic Field (B).

Q2: What is the SI unit of magnetic field?

Answer: Tesla. Another unit is Newton Ampere-1 metre-1

Q3: What is a solenoid?

Answer: A solenoid is a circular coil of a large number of turns, such that the turns of solenoid run parallel to its length. It acts similar to a bar magnet.

Q4: What is Lorentz force?

Answer: The total force on a charge (q) moving with a velocity (v) in the presence of magnetic and electric field (B and F) respectively is called Lorentz force.

Q5: What is a cyclotron?

Answer: It is a machine to accelerate charged particles or ions to high energies

Q6: What is the operational definition of one ampere?