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college physics

The Maxwell’s Equations, from nature to instruments.

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The beauty of Maxwell’s equations can be seen in how it helps us understand nature as well as instruments, at the same time. Medical devices are simply an advanced understanding that began with understanding electromagnetic waves through Maxwell’s equations.

Each of the following 4 equations has a different name, by which we call’em, but together they are called as the Maxwell’s equations. Together they constitute what I am inspired to say; the golden equations of Physics. If we do some easy tricks they will be converted into whats called as the Wave Equations (of motion) ! Yes, they describe the wave behavior “fully”.

— By that I don’t mean sound waves, but any sort of waves that move at the speed of light. Sound waves are ordinary pressure oscillations, that travel much slower than even rockets.
The 4 equations therefore describe how electromagnetic waves are created and broadcast. Hence TV radio and satellite communication were understood because these 4 equations were understood.

First two are time-independent or static equations.

The first equation is known as Gauss’s law of electrostatics and says “Electric fields (E), are a result of sources of electrostatic charge”.

The 2nd equation is analogous and called as Gauss’s law of static magnetic field. But it says “apparently there are no sources of magneto-static charge or single magnetic pole from which the magnetic field B is created”.

Then how are magnetic fields created? We needed to know further to find the answer. Lets look at the 3rd and 4th equations.

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Coriolis Force; An interesting idea.

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I have been thinking of writing a basic introduction, on this important physical concept — of, what’s a Coriolis Force.

Its one of the interesting ideas of physics, which does not get as much of a mention, unless you just happen to know this, because of your advance footing, in the discourses of Physics; perhaps because its two orders of magnitude smaller, in its strength, compared to relevant forces, in a situation, that involves this small — but, significantly measurable force.

So, what’s a Coriolis Force?

I presume that most of us would be aware of, what’s centrifugal force. Its in this connection, that, a Coriolis force is most understandable.

So, what’s a centrifugal force?

A Centrifugal force, comes into picture, every time a centripetal force comes into consideration. A centrifugal force is the corresponding pseudo force, of a centripetal force. So, for every centripetal force there would be a corresponding centrifugal force.

So, we need to shed light on a few things, before we understand, what are Coriolis Force. We need to therefore discuss; what are pseudo forces and what’s a centripetal or a centrifugal force, then a coriolis force would be clearer, to the root.

So lets begin with Force.

Force has a basic standing in Physics, in connection to, in what frames of reference we need to measure such a physical quantity, as are all other physical quantities to be measured, have a significance, as to; in what frames of reference we are measuring these quantities in.

A Question a Day (series) Q3

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The equation v = a*del_t is sometimes used
to find velocity when acceleration and
time are known. Another form of this
equation is v = v_0 + a*del_t. In this second
form of the equation, the function of the
term v_0 is to:

A. indicate that the equation is valid
only for an object that starts at rest.

B. determine the time at which
velocity is equal to zero.

A Question a Day (series) Q2

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1. A ball is thrown with an initial velocity of 20 m/s at an angle of 30°
above the horizontal. What is the instantaneous vertical velocity of
the ball when it is 5.1 m above the release point? (g = 9.8 m/s^2)

A. 0.2 m/s
B. 6.6 m/s
C. 10 m/s
D. 17 m/s

Physics Class Test, XII {PU/ISc/ICSE/CBSE}

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A. What’s the speed of an electron in a cathode ray tube if the electric field and magnetic field are of unit strength in SI unit? Calculate magnetic force experienced by the electron. 4 marks
B. Derive the formula for magnetic field produced by an infinitely long straight conductor. 4 marks

Physics Midterm for ISc-II (ICSE) [also good for CBSE/PU-II]

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(c) Fission of U – 235 nucleus releases 200 MeV of energy. Calculate the fission rate (i.e. no. of fissions per second) in order to produce a power of 320 MW.

Q 10:

(a) What’s the ratio of the shortest wavelength of Balmer series to the shortest wavelength of the Lyman series?

(b) What are the (i) energy (ii) magnitude of momentum, and (iii) wavelength of the photon associated with spectral emission of H-atom transition; n=3 state to n=1 state?

I.S.C. Board Question Paper. Physics, Class XII – 2009 ( C.I.S.C.E. )

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Question 1 
Answer all question briefly and to the point.

(i)
Explain the statement ‘relative permittivity of water is 81’.

(ii)
Draw (at least three) electric lines of force due to an electric dipole.

(iii)
Find the value of resistance X in the circuit below so that the junction M and N are at the same potential.

(ix)
A ray LM of monochromatic light incident normally on one refracting surface AB of a regular glass prism ABC emerges in air from the adjacent surface AC as shown in Figure. Calculate the refractive index of the material of the prism.

SECTION A
(Answer any two questions)

Question 2 
(a)
With the help of a labeled diagram, obtain an expression for the electric field intensity ‘E’ at a point P in broad side position (i.e. equatorial plane) of an electric dipole.

Question 3
(c)
(i) State any two differences between a moving coil galvanometer and a tangent galvanometer.

(ii) What is the use of a Cyclotron?

SECTION C
(Answer any two questions)

Question 8
(a)
Electrons, initially at rest, are passed through a potential difference of 2 kV. Calculate their:

(i) Final velocity and

(ii) de Broglie wavelength

Physics midterm exam, for class XII (ISC-II) for C.I.S.C.E. board.

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PART-I
Total 10 marks
Each question carries 1 mark.  Answer all. (10)              

Question 1 [Objective, 10 X 1]
(a)
Which of the following drops faster?

A. an electric dipole‘s electric field                      B. an electric dipole‘s electric potential

C. a point charge’s electric field                            D. a point charge’s electric potential

Physics midterm, for class XII, for C.B.S.E. and State boards.

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Question 1
Which of the following drops faster?

A. An electric dipole’s electric field                      B. An electric dipole’s electric potential

C. A point charge’s electric field                            D. A point charge’s electric potential

Question 4
Chose the correct one

A. Kirchhoff’s loop rule is applied to a junction of incoming and outgoing current?

B. According to Kirchhoff’s loop rule a junction of incoming and outgoing current carries a potential proportional to the amount of current flowing through the junction.             

C. Kirchhoff’s junction rule can be applied to a single current carrying path in any electric circuit.

D. The potential drop in a loop in any electric circuit is zero and its based on conservation of energy.

Question 5
Chose the correct one

A. Resultant of capacitance in series is more than individual resistances

B. Current division works on the basis of direct proportionality of resistances

C. Voltage division works on the basis of direct proportionality of resistances

D. Resistors in series will add up

PART-B

Question 2
Describe de-Broglie wavelength in 1 or 2 lines and write the formula that we use for this idea.

Question 6
Give example of 3 conservative forces. A conservative force is defined through the following; “The work done in a conservative force field during a circular voyage is zero, as such work done are independent of the path taken”.

PART-C

Question 1
Define electric current and electric current density. State and explain Ohm’s law. Derive an expression for drift velocity.

Question 7
Derive the magnetic field B of a toroid by using Ampere’s circuital law.

PART-D

Question 13.
State the mirror equation and thin lens formula. Derive the lens formula with a suitable diagram.

Physics midterm preparatory exam, (+2) 2nd year, C.B.S.E. and state boards.

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PART-A
Answer all the following questions, 1 mark each, 1 X 10
Question 1
Which of the following is a vector?

A. An electric dipole’s electric potential          B. An electric dipole’s charge

C. Electric current                                                D. Electric current density

Question 2
Which medium will have a stronger electrostatic force between 2 charges?

A. Medium with ε = 12                                      B. Medium with ε = 102

C. Medium with ε = 81                                      D. Free space, ε = ε0.

Question 3
Pick only the correct one “between an electron and a positron”

A. The electron has more specific charge.

B. The positron has more specific charge.

C. Both have equal specific charge.

D. For some particles specific charge can’t be determined, so it can’t be said electron or positron has more specific charge.

Question 4
Chose the correct one

A. Kirchhoff’s loop rule is applied to a junction of incoming and outgoing current.

B. According to Kirchhoff’s loop rule a junction of incoming and outgoing current carries a potential proportional to the amount of current flowing through the junction.             

C. Kirchhoff’s Junction rule can be applied to a single current carrying path in any electric circuit.

D. The potential drop in a loop in any electric circuit is zero and its based on conservation of energy.

Question 5
Chose the correct one

A. Resultant of capacitance in series in more than individual resistances

B. Current division works on the basis of direct proportionality of resistances

C. Voltage division works on the basis of direct proportionality of resistances

D. Resistors in series will add up

Physics midterm preparatory exam, ISC-II, C.I.S.C.E.

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PREPARATORY CLASS EXAMINATION FOR MIDTERM – 2013
(16 Aug 2013)

PHYSICS
PAPER I
(THEORY)
(Three hours)

Candidates are allowed additional 15 minutes for only reading the paper.

They must not start writing during this time

Answer all questions in Part I and eight questions in Part II, choosing two questions from each of the three sections A, B and C.

All working including rough work should be done on the same sheet as, and adjacent to, the rest of the answer.

The intended marks for questions or parts of questions are given in brackets [  ].

PART I
Question 1 [ Objective ]
Total 10 marks
Each sub-question carries 1 mark.  Answer all. 

(a)
Which of the following is a vector?

A. An electric dipole’s electric potential          
B. An electric dipole’s charge
C. Electric current                   D. Electric current density

(c)
Pick only the correct one “between an electron and a positron”

A. The electron has more specific charge

B. The positron has more specific charge

C. Both have equal specific charge

D. For some particles specific charge can’t be determined, so it can’t be said electron or positron has more specific charge

(d)
Chose the correct one

A. Kirchhoff’s loop rule is applied to a junction of incoming and outgoing current

B. According to Kirchhoff’s loop rule a junction of incoming and outgoing current carries a potential proportional to the amount of current flowing through the junction          

C. Kirchhoff’s Junction rule can be applied to a single current carrying path in any electric circuit

D. The potential drop in a loop in any electric circuit is zero and its based on conservation of energy

(e)
Chose the correct one

A. Resultant of capacitance in series in more than individual resistances

B. Current division works on the basis of direct proportionality of resistances

C. Voltage division works on the basis of direct proportionality of resistances

D. Resistors in series will add up

PART II
Total 50 marks (Optional, 6 out of 9. Compulsory 2) 

SECTION A
This question is compulsory  ( total 7 )

Question 2
Define electric current and electric current density. State if these two quantities are scalar or vector quantities and explain why. State and explain Ohm’s law. Derive the Ohm’s law in vector form from the scalar form. Write the expression for drift velocity.

Physics class tests for junior college, –III

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Physics class tests for PUC, ISc, XII in the CBSE, ICSE (CISCE), State boards.
Subject: Physics                                         
Test: Class test — III
Class: PUC — II (also good for ISC — II)
date: 5th August 2013.
Time: 55 minutes 
Total marks: 35

Section A
Objective — 7 questions each carry 1 mark, all questions to be answered.

Question 1
Targets in X-ray tube are made of high atomic number metals. Examples are

A. Tungsten and Platinum              B. Nickel and Chromium

C. Uranium and Plutonium            D. Sodium and Mercury

Question 2
Electric and magnetic fields do not deflect which of the following

A. X-rays                    B. Y-rays

C. Electrons              D. Cosmic Rays

Question 3

Physics class tests, XII/ICSE/CBSE

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3. Why Ka and Kb lines are produced (chose only one appropriate answer)

A. electronic transitions B. Atomic collisions

C. Radioactive decay D. Nuclear transmutation

4. Exactly why there is quantization of physical variables such as momentum, angular momentum, energy, orbital distance and speed?

A. wave-particle duality B. Interference of waves

C. Particle acceleration to speed of light D. Resistance experienced by particles in conductors

5. Cathode rays are streams of

A. electrons B. x-rays

C. nucleons D. high atomic number elements

Physics class tests for XII/ICSE/CBSE

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Question 1

Derive potential due to an electric dipole in a general direction making an angle J with dipole axis. Use E = -dV/dr to obtain E in general direction.

Question 2

Derive electric field in the end-on and broad-on position for a dipole vector P = p 2Q.a, where P is the vector and p the unit vector along the same.

Question 3

Describe the Rutherford’s model of the atom. Explain the results of the Geiger-Marsden experiment with a diagram. Mention the Rutherford’s model’s drawback.

Physics class tests for junior college, –I, II

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Physics class tests for PUC, ISc, XII in the CBSE, ICSE (CISCE), State boards.

Class test — I

Subject: Physics
Test: Class test — I
Class: ISC — II, PUC — II

Question 1
Whats the unit of capacitance?

Question 2
What is the amount of work done on an equipotential surface?

Question 3
Between an alpha-particle and a proton which has more energy in a 100-Volt region?

Question 4
Which is correct for a series combination of capacitance? …

Homework questions of Physics for Junior college (PUC, ISc, XII, CBSE, ICSE)

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Question 3

Deuteron is a bound state of a neutron (n) and a proton (p) with a binding energy BE = 2.2 MeV. A g-ray of energy E is aimed at a deuteron nucleus to try to break it into a neutron and proton so that n and p move in direction of incident g ray. If E = B.E. show that this is not possible. How much should BE be so that such a process can occur.

Question 4

Total charge –Q is uniformly distributed along length of a ring of radius R. A small test charge = q of mass m is kept at center of ring and is given a gentle push along the axis of the ring.

Physics Preparatory Test for Quarterly, Class XII, –I

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Question 1
What’s the work done to take a charge Q on a circular voyage, on an equipotential surface?

A. Zero
B. Depends on radius of circle
C. Depends on distance from center of equipotential surface       
D. Q/epsilon_0

Rutherford’s atomic model is based on which fact

A. Geiger Marsden scattering of alpha-{particles} suggests presence of nucleus.

B. Smith’s electrodes dipped in electrochemical material

C. Quantization of charge     D. Quantization of angular momentum

Question 6
What’s the typical energy output range of Indian nuclear reactors?

Question 7
Which of the following physical quantity is scalar: electric field intensity, electric potential, dipole moment?

Question 9
Use superposition principle of electric field intensity of two charges, to obtain the electric field intensity E of a dipole along the dipole axis. This is known as electric field for the End-on configuration.

Also use the same idea to obtain the potential at a point vertical to the dipole axis. This is known as potential for the Broad-on configuration. 

Question 10
Obtain the electric field intensity E of a dipole vertical to the dipole axis, i.e. — Broad-on electric field. Also obtain the potential at a point on the dipole axis, i.e. — End-on potential.

Question 17
Describe the Van-de-Graaff generator, its principle, working and use.

Physics Preparatory Test for Quarterly, Class XII, –II

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Physics preparatory tests for PUC, ISc, class XII in the CBSE, ICSE (CISCE), State boards.
Subject: Physics            

Test: Preparatory test — II. Pre-Quarterly.
Class: PUC — II (also good for ISC — II)
date: 25 the June 2013.
Time: 1.5 hours.
Total marks: 50

Instructions.

— Numerical problems solved without writing the relevant formulas carry no marks.

— Answers without relevant diagrams, circuits wherever necessary will not carry any marks.

PART-A
I. Answer all the following questions (1 X 5)
Question 1
Where would Coulomb’s interaction be weaker, in dielectric medium or vacuum?

Question 2
Between a dipole and a point charge whose electric potential reduces faster?

Question 3
What is the work done when a charge makes a rectangular path on an equipotential surface?

Question 4
Write the de-Broglie formula for wavelength of a wave-particle if its momentum is p?

Question 5
Define refractive index from angle of incidence and angle of reflection.

PART-B
II. Answer any Five of the following questions, 2 marks each.   (2 X 5=10)
Question 6
State how density of electric lines of force is related to the electric field vector intensity E. Also mention another property of the lines of force and one property of the equipotential surface.

Question 7
Write the Gauss law of electrostatics and define electric flux for a uniform field E.

Question 8
How one defines the direction of a dipole vector? What’s the potential vertical to the dipole axis?

V. Answer any three of the following questions (5 X 3)
Question 19
A proton has a radius R and the charge Q is uniformly distributed. Use Bohr’s atomic energy level formula for the 1st excited state (n = 2) and ground state (n = 1) to obtain energy of the Hydrogen-atom.

Question 21
Draw a simple and neat diagram showing a convex lens, optical center and focal point (focus). Now define power of a lens and obtain an expression for it.

Class XII, ICSE exam questions, Physics, Updated Version 2

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Question 6 [2+3+2]

Obtain an expression for the Nuclear Size of an atom by solving for distance of closest approach (r) which is also known as Impact Parameter (say l). Use an incoming alpha-particle of mass mα and charge q that’s deflected by the presence of a nucleus of atomic number Z to obtain l. Now replace the variables by some numerical: mα = 6.8×10-27kg, e = 1.6 x 10-19 coul, Z=14, and vα= 2.0×107 m/s. Express the answer in Femto-meters.

Question 7 [3+4]

A proton has a radius R and the charge Q is uniformly distributed. Use Bohr’s atomic energy level formula for the 1st excited state {n=2} energy of the Hydrogen-atom.

Class XII, CBSE exam questions, Physics

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Electrostatics

6. State how density of electric lines of force is related to the Electric Field Vector intensity E. Also mention another three properties of the lines of forces.

7. Write the vector expression for Coulomb’s law and state 3 forces that are conservative forces by nature.

8. What happens to the charge on a conducting shell? What happens to lines of forces when a conducting shell is present in the path of the lines of forces?

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