TyroCity: Physics Notes

Magnetic Properties of Materials

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

What are magnetic domains?
What is angle of dip? How does it vary from the equator to the poles/
Define angle of dip and angle of declination at a place.
How does dip vary from place to place on earth`s surface?
Why does a bar magnet not retain its magnetism when it is method?
Why does a magnet lose its magnetism when heated to high temperature?
Above Curie temperature a ferromagnetic material becomes paramagnetic. Why?
What are the characteristics of a Ferro-magnetic substance?
A permanent magnet can be used to pick up a string of nails, tacks or paper clips, even though these are not magnets by themselves. How can this be?
A ferromagnetic substance becomes paramagnetic above Curie temperature. Explain why?

Long Questions

The angle of dip in Britain is greater than that in Kathmandu. Why?

Electrical Circuits

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

State Kirchhoff`s laws of circuits.
Why does voltmeter measures current more accurately than an ammeter?
What is Wheatstone bridge? Obtain the balanced condition for the bridge? Explain how resistance can be measured by a meter bridge?

Long Questions

What is a Wheatstone bridge? Using Kirchhoff`s law, derive the principle of Wheatstone bridge.
What is a potentiometer? Explain how you compare the emfs of two cells using a potentiometer.
Discuss the principle of potentiometer and use it to determine the internal resistance of a cell.
Discuss the principle of the potentiometer and use it to compare the emfs of two cells.
Explain the principle of the potentiometer. How is this used to measure the internal resistance of a cell?
State and explain Joule`s law of heating. Deduce an expression for the heat developed in a wire by the passage of an electric current?
What is potentiometer? How can you use it to measure internal resistance of a cell?
What is internal resistance of a cell? How can you measure the internal resistance of a cell by using potentiometer?
What is the principle of potentiometer? Describe a method to measure the internal resistance of a cell by using potentiometer.
What is Wheatstone bridge? Derive the principle of Wheatstone bridge using Kirchhoff`s Law.

Acoustic Phenomena

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Answer Questions

How are beats produced? What is beat frequency?
What are ultrasonic and infrasonic?
Distinguish between ultrasonic and supersonic’s.
How it is that one can recognize a friend from his voice without seeing him?
Why is it roaring of a lion different than the sound of a mosquito?
What do you mean by the term threshold of hearing?
Whistle of an approaching train is shriller. Why?
Define beats and beat frequency.
Bells are made of metal and not of wood, why?
Explain with a figure the meaning of beats.
Two notes, one produced by violin and the other by a sitar, may have the frequency, yet we can distinguish between them. Why?
Which has a more direct influence on the sound wave: the observer is approaching the stationary sound source.
What is meant by threshold of hearing?

Long

Deduce the expressions for the frequency herd by an observer, when the observer is approaching the stationary sound source.
What is Doppler`s effect? Derive an expression for the apparent frequency received by a stationary observer when a source is moving away from him.
What do you mean by intensity and intensity level of sound? Define bel and decibel.
What are beats? Prove that the number of beats per second is equal to the difference between the frequencies of two superposing waves.
What is Doppler`s effect? Derive the change in frequency when an observer moves towards a stationary source?
Discuss the phenomenon of Doppler`s effect. Find the change in frequency when a moving source of sound passes a stationery observer.
Define intensity of sound. Show that the intensity of sound for a given frequency is directly proportional to the square of amplitude of vibration.

8 Define the intensity of sound and prove that l=1/2pVr2w2 where the symbols have their usual meaning.

What is the Doppler Effect in sound? Obtain an expression for the apparent frequency of the sound when the source and observer both move in the same direction.
Define intensity and deduce it in terms of amplitude of vibration, density of medium, angular velocity and velocity of the wave.
What are beats? Obtain an expression for the beat frequency when beats are produced by superposing two waves of slightly different frequencies.
What is Doppler`s Effect? Deduce an expression for the apparent frequency heard by a stationary observer when a source approaches towards him.

Mechanical Waves: Important Questions

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

What do you mean by water waves?
Why sound produced at a distance can be heard distinctly at night than in day time?
Is velocity of sound more in damp air or in dry air? Explain.
A boat at anchor is rocked by waves whose crest is 100 feet apart and whose velocity is 25 feet /s. These reach the boats once in every t s. What is the value of t?
Ultrasonic, infrasonic and audio waves travel through a medium with velocity vu, vi, varespectively. Then what is the relationship among them?
A man stands on the ground at a fixed distance from a siren whit emits a sound of fixed amplitude.
The ratio of velocity of sound in hydrogen gas r=7/5 to that on helium gas r= 5/3 at the same temperature is VH:VHe, what is the value of this ratio?
The velocity of sound in a tube containing air at 27°C at the pressure of 760 cm of Hg is 330 m/s. What will be the velocity of sound when the pressure is increased to 100 cm of Hg and temperature is kept constant?
A uniform rod of length L and mass M hangs freely from a fined point. Then the velocity of transverse wave along the rod at a distance x from the free end is v m/s. What is its value?
In a ripple tank when one pulse is sent every 10th of a second, the distance between consecutive pulses is 30 mm. in the same depth of water pulse are produced in half second intervals. What is the distance between consecutive pulses?
If you are walking on the moon surface, can you hear the cracking sound behind you? Explain.
Do sound waves need a medium to travel from one point to other point in space? What properties of the medium are relevant?
Why velocity of sound in solid is more than that in liquid?
Why velocity of sound in liquid is more than that in air?
Why velocity of sound in hydrogen is more than that in air?
What are the draw backs of Newton’s formula for the velocity of sound in air? What is the Laplace’s correction?
What is the sound of clock tower heard feebly at large distance than near to it?
What is beat? How a musician can use this effect to tune string instrument?
What is threshold of hearing and threshold of pain?
Why are beats produced? What is beat frequency?
What is it that one can recognize a friend from his voice without seeing him?
Whistle of an approaching train is shriller. Why?
Although the density of solid is high, the velocity of sound is greater in solid, explain.
Why is roaring of the lion different than that of mosquito?
What is persistence of hearing? Also define threshold of hearing (or audibility) threshold.
Why is the wall at the back of the stage in a big hall made parabolic?
A stone is dropped from the top of the tower 300m high splashes into the water of a pond near the base, of the tower. When is the splash heard at the top? Given that the speed of sound in air is 340 m/s, g= 9.8 m/s [ ans= 8.70 s]
The audible frequency range of a human air is 20Hz to 20KHz. Convert this into the corresponding wavelength range. V of sound on air = 340 m/s.
Draw the graph for beat phenomenon.

Free question test - Physics 12

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Current Electricity

Discuss the mechanism of metallic conduction. Derive a relation between current density and drift velocity.
How is a galvanometer converted into an ammeter and to voltmeter? Explain?
Distinguish between resistance and resistivity. Derive expression for the effective resistance of number of resistors, connected in series and parallel.
Wave and Sound
What is resonance? How is the velocity of sound in air determined by resonance tube method?
What is the principle of super position as applied to wave motion? Discuss, the result of superposing two waves of equal amplitude and same frequency travelling in opposite direction.
What do you mean by phase oscillation and phase constant? Establish the equation of progressive wave.
Magnetic Effect if Current
Define radial magnetic field. Derive an expression for the torque on a rectangular coil in a uniform magnetic field and mention the condition for maximum and minimum torque.
Derive an expression for the magnetic field intensity at a point due to a current carrying straight conductor of infinity length, using Biot-Savart law.
Obtain an expression for the torque acting on a rectangular coil in a uniform magnetic field and also define magnetic moment.

Modern Physics

Describe J.J. Thomson’s experiment for determining the specific charge of an electron.
Describe the phenomenon of electrical discharge through gases.
Describe with necessary theory of Millikan’s oil drop experiment to determine the value of the charge particle in electric and magnetic field.
Discuss the productivity of cathode ray and its characteristics.

Physics XII Questions

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Unit 1: Waves and Optics

Waves

Physical Optics

Unit 2: Electricity and magnetism

Current Electricity

Magnetic Field of current

Other topics

Free question test - Physics 12

Diffraction

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Diffraction grating is better than a two –slit set up for measuring the wave length of monochromic light. Explain.
What is diffraction of light?
Radio waves diffract around building but light waves do not. Why?
The diffraction of sound waves is more evident in daily experience than that of light waves, why?
Describe what happens to the single slit diffraction pattern when the width of the slit is less than the wave length of the wave.
What is self-inductance? Define coefficient of self-inductance.
What is diffraction of light? How does it differ from interference of light?
Describe the diffraction of light at a single slit and find the condition for secondary maxima and minima.
What are the difference between interference and diffraction? Explain the theory of diffraction off light through a single slit.
Describe diffraction of light through a single slit.
What is the basic difference between interference and diffraction? Discuss Fraunhofer diffraction at a single slit.
What is Fraunhoffer diffraction? Explain the formation of maxima and minima due to diffraction? Show that the width of central maxima is inversely proportional to the distance between the two slits.

Gravitation

TyroCity.com — Sat, 12 Jul 2014 05:41:42 +0000

Gravitation
Every object in our universe attracts the other object with certain force towards its center. This force of attraction is known as GRAVITATIONAL FORCE and the phenomenon is called GRAVITATION. This is gravitational force which is responsible for the uniformity or regularity in our daily astronomical life. The whole system of the universe is in order only due to this force. Due to gravitation, the system of our universe is working uniformly and smoothly. The planets around the earth or around the sun moves in an orderly motion due to gravitation.

Newton's Law of Gravitation

In order to explain the gravitational force between two bodies, Newton formulated a fundamental law known after his name i.e. “NEWTON’S LAW OF GRAVITATION”

Newton’s law of gravitation states thatevery object in the universe attracts the other object with a force and :

(1) The gravitational force of attraction between two bodies is directly proportional to the product of their masses.

F a m1 x m2 ——- (1)

(2) The gravitational force of attraction between two bodies is inversely proportional to the square of the distance between their centers.

F a 1/r² ——— (2)

Mathematical Representation

Let us consider two bodies of masses m1 and m2 placed with their centres at distance of r from each other.

According to the Newton’s law of gravitation, the gravitational force of attraction between them is

F a m1 x m2 ——- (1)
F a 1/r¹ ——— (2)
F a m1m2 /r¹

Combining (1) and (2)

F = G m1m2/r¹

Where is the constant of proportionality.

G = universal gravitational constant

Value of G:

G = 6.67 x 10^-11 Nm²/kg²

Vectoral form of the law

The law of universal gravitation can also be expressed in vector form, which gives the magnitude as well as the direction of gravitational force.

The force exerted on body (1) by body (2) is always directed towards body (2) and acts along the line joining their centres
The displacement vector "r" from (2) to (1) is directed from body (2) to body (1), then,

The force exerted on body (2) by body (1) is always directed towards body (1) and acts along the line joining their centres
The displacement vector "r" from (1) to (2) is directed from body (1) to body (2), then,

The negative sign shows that the force of gravitation between two bodies is always an attractive force not a repulsive force.

Wave Motion

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Wave motion

Short Questions

How are stationary waves formed?
If you are moving on the moon surface, can you hear the cracking sound behind you? Explain.
Do sound waves undergo reflection, refraction and polarization phenomena? Explain.
Which type of wave propagates in liquid, explain.
Longitudinal waves cannot be polarized. Why?
Distinguish between light waves and sound waves.

Long Questions

Use the principle of superposition of two waves to find the position of displacement of nodes and antinodes in standing waves?
State and explain the stationary waves?
Define progressive wave. Derive progressive wave equation.
What do you mean by progressive wave equation? Derive progressive wave equation in terms of its wave vector and displacement.
What the principle of superposition is as applied to wave motion? Discuss, the result of superposing two waves of equal amplitude and same frequency travelling in opposite direction.

Thermoelectric Effect

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

What do you mean by Peltier`s effect?
What is thermoelectric emf?
Why is Sb-Bi thermocouple preferred to Fe-Cu thermocouple?
What are the factors on which the thermo emf produced in a thermocouple depends?
How is Seebeck effect different from Pektier effect? Explain.
How does thermo emf change in thermocouple when the temperature of the hot junction is changed?
What are the factor on which thermo-emf depend?
Define temperature of inversion. On what factors does it depend?
What do you mean by thermoelectric effect?
Does the thermo-electric effect obey the Law of conservation of energy? Explain.

Long Questions

What do you mean by Seebeck Effect? How thermoelectric e.m.f. does vary with the temperature?
What is Seebeck Effect? How does the emf of a thermocouple vary with temperature of the hot junction?
How does the thermo efm of a thermocouple vary with temperature of the hot junction?
What is thermoelectric effect? Discuss the variation of thermo-efm with the change in temperature of the hot junction.

Interference

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Answer Questions

Can two independent sources of light produce interference?
Why have the two sources of light to be close to each other for the production of good interference pattern?
Distinguish between interference and diffraction. What do you understand by coherent sources?
In young’s double slit experiment, how is the fringe width altered if the separation between the slits is doubled and the distance between the slits and the screen is halved?
What are the conditions for sustained interference of light?
In Young’s double slit experiment, how is the fringe width altered if the separation between the slits is doubled and the distance between the slits and the screen is halved?
What do you understand by the coherent sources of light?

Long Answer Questions

Derive the fringe width from Young’s double slit experiment.
What do you understand by interference of light? Derive an expression for the fringe width in a Young’s double slits experiment.
Describe Young’s double slits experiment for the interference of light and show that widths of bright and dark fringes are the same.
Prove analytically that the bright and dark fringes in young’s double slit experiment are equally spaced.
Draw a clear ray diagram to illustrate the action of a compound microscope. Also derive an expression for its magnifying power.
Describe Young’s double slit experiment, if brief, for the measurement of wave=length of a monochromatic source of light.
Where is the near point of an eye for which a spectacle lens of power +2D is prescribed?

Electromagnetic Induction

Physics XII Notes — Sat, 12 Jul 2014 05:41:42 +0000

Short Questions

What is Lenz’s law?
Mention two types of loss in a transformer.
Show that Lenz’s law is an example of conservation of energy.
Two closely would circular coils have the same number of turns, but one has twice the radius of the other. What is the ratio of self inductance’s of the two coils?
Why can`t a transformer be used to change the value of d.c. voltage?
What is eddy current? Write down its uses?
What are different power losses in a transformer? What measures do you take to minimize these losses?
Why can`t a transformer be used to step up or down the d.c. voltage?
A transformer cannot be used in do circuits, why?
State Faraday`s laws of electromagnetic induction.
A sheet of copper is placed between the poles of an electromagnet with the magnetic field perpendicular to the sheet. When it is pulled out, a considerable force is required, and the force required increases with speed, why?
Permanent magnets are made of steel while the core of transformer is made of soft iron. Why?
A student asserted that if a permanent magnet is dropped down a vertical copper pipe, it eventually reaches a terminal velocity even if there is no air resistance. Why should this be?
If a permanent magnet is dropped down a vertical copper pipe, it eventually reaches a terminal velocity even if there is no air resistance. Why should this be?
Describe the theory and working of an a.c. generator.

Long Questions

Obtain the expression for the emf induced in the conductor moving in a magnetic field.
State the laws of electromagnetic induction. Derive an expression for the emf induced in a conductor moving in a magnetic field.
Deduce an expression for induced emf in a coil rotating in a magnetic field.
State Lenz`s law and explain how this law leads to the conservation of energy principle.
State Faraday`s laws of electromagnetic induction. Deduce an expression for induced emf in a coil rotating in a magnetic field.
State and explain Faraday`s law of electromagnetic induction. Derive an expression for the induction a coil rotating in a uniform magnetic field.
State Faraday`s law of electromagnetic induction. Derive an expression for the induced in a straight conductor moving at right angle to the direction of a uniform magnetic field.
A metallic rod is moving in a magnetic field. Determine the emf induced across it.