ELECTROSTATICS

How was your Physics Practical Examination?

Hello students!

It’s the time of AISSCE Practical Examination.

How was your Physics Practical Examination and Viva?

Which questions were asked to you?

Which were the experiments and activities you were asked to perform?

How farely did you do it?

Share your experience here as comments to this post. Your responses will be a boon for the others.

You can post the questions you were asked during Viva so that others can find the answers to them and learn for the Viva during their turn.

Class 12 Physics : Electrostatics Revision Test

Max marks:50 Time:2hrs

1. A glass rod rubbed with silk acquires a charge of 6×10^-12 C. Calculate the number of electrons it has gained or lost. (1)
2. If the magnitude of each charge becomes doubled, the separation between them is halved and the system of charges kept in a medium of=3 Calculate the force between them. (1)
3. If two equal charges separated by a distance of 2m in air medium experiences a force of 0.9×10¹⁰ C, Calculate the magnitude of each charge. (1)
4. Electric field intensity is 400Vm^-1 at a distance of 2 m from a point charge. At what distance it will become 100 Vm^-1? (1)
5. What will be the force experienced by a particle of charge 2µC placed in an electric field of 10kVm^-1? (1)
6. What is the work done by moving 400μF charge between two points separated by a distance of 27 cm on an equipotential surface? (1)
7. Calculate the number of electric lines of force from a charge 1.7708X10^-6 C in air medium? (1)
8. Two protons ‘A’ and ‘B’ are placed between two parallel plates having a potential difference ‘V’ as shown in the figure. Will these protons experience equal or unequal force? (1)
9. Draw an equipotential surface for a point charge q> 0(1)
10. The capacitance of a parallel plate capacitor is ‘C’. If 15 such capacitors are connected in series and then in parallel, what is the ratio of effective capacitance of first case to the second? (1)
11. What is electric polarization ,polar and non polar molecules?( 2)
12. 2) Define electrostatic induction and corona discharge. ( 2)
13. Calculate the ratio of force experienced by a proton to that of the electron placed in an electric field of 4KVm^-1. ( 2)
14. If an electrician has three capacitors of capacitances 4µF, 7µF& 12µF. How should he connect them, So that the effective capacitance will be 10µF? ( 2)
15. Define the SI unit of potential difference and charge. ( 2)
16. Two charges of 20µC and -20µC are placed 20 cm apart at points A and B respectively. Compute the electric field strength at point C, 20 cm away from both A and B.(3)
17. Three capacitors of capacitances 4µF, 6µF and 8µF are connected parallel to each other and the combination is connected across a battery of 25V. Calculate the charges present on each capacitor and the total charge flows from the source. (3)
18. Derive an expression for the torque experienced by a dipole in an external electric field. (3)
19. Obtain an expression for the capacitance of a parallel plate capacitor. (3)
20. Derive the relation E= (3)
21. Derive an expression for the potential at a point due to dipole. Write the special cases also.(5)
22. Derive an expression for ‘E’ at a point on the axial line of the dipole. (5)
23. Explain with a neat diagram the principle, construction and working of a Van de Graff generator. (5)

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How atoms are formed? – Neeraj Asks

Neeraj asks: ”We have read that atoms can neither been created nor been destroyed!I want to know from where atoms came in existence,if they can not been created,also atom contain electron and proton which are negatively and positively charged,i want to know from where these charge came?”   Your question will be answered soon Link to this post!

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How atoms are formed? – Neeraj Asks

Neeraj asks: ”We have read that atoms can neither been created nor been destroyed!I want to know from where atoms came in existence,if they can not been created,also atom contain electron and proton which are negatively and positively charged,i want to know from where these charge came?”   Your question will be answered soon Link to this post!

Read more...

Electrons and flow of electrons – Did you have this doubt before?

“When an electric cell is connected to a circuit, electrons flow away from the negative terminal in the circuit. But within the cell, electrons flow to the negative terminal. Explain? Answer: The question seems to be the result of some misconceptions. If we consider an electrochemical cell, it is the chemical reactions which develops and ...Read the full post

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What is meant by charge on a capacitor?

Mohit asked this question:

“What is meant by charge on a capacitor?”

Answer: As we know, a simple capacitor (say a parallel plate capacitor) consists of two plates parallel to each other. When charged, charge on either plate of the capacitor is called charge on the capacitor.

The following links will help you explore further and understand more

• http://www.kpsec.freeuk.com/components/capac.htm
• http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capac.html
• http://www.youtube.com/watch?v=zNpbdptwxlQ
• http://www.youtube.com/watch?v=qdXbnhb1bVo&feature=related

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]