MCQs

1. A body of mass 1 kg carrying a charge of 1 coulomb falls in an electric field through a potential difference of 1 volt. Its velocity is

1. [latex]1\ ms^{-1}[/latex]
2. [latex]2\ ms^{-1}[/latex]
3. [latex]0.5\ ms^{-1}[/latex]
4. [latex]1.4\ ms^{-1}[/latex]

CONCEPTUAL PROBLEMS

1. Define electric field and electric field intensity.
2. Can two electric lines of force intersect each other? Explain.
3. What is the magnitude of an electric field which will balance the weight of an electron on the surface of earth?
4. Two positive charges separated by a distance create an electrostatic field. Can electric field intensity be zero at a point between the charges? Justify your answer.
5. Under what conditions, the electric lines of force are curved?
6. A charge particle is free to move in an electric field. Will it always move along an electric lines of force?
7. When an iron plate is placed between two charges, what will be the electrostatic force of attraction between them?
8. An electron and a proton are placed in a uniform electric field; will their acceleration be same?
9. What will be the electric field strength at a point mid-way between two equal and opposite charges?
10. State gauss theorem. What is Gaussian surface?
11. Would Gauss law be helpful for determining the electric field of a dipole?
12. Why do the electrostatic field lines not form closed loops?
13. Draw lines of force to represent a uniform electric field.

THEORY BASED PROBLEMS

14. State Gauss’s theorem in electrostatics. Use this theorem to calculate electric field due to a solid charged sphere at a point inside it.
15. State and explain Gauss’s theorem in electrostatics and use it to find the electric field intensity due to a hollow charged spherical conductor.
16. State and explain Gauss’s theorem in electrostatics. Use it to obtain an expression for electric field intensity due to a linearly charged body.
17. State and explain Gauss’s theorem in electrostatics. Use this theorem to find the electric field intensity due to a plane charged conductor.

NUMERICAL PROBLEMS

1. Two large parallel metal plates carry opposite charges. They are separated by 0.20 m and the p.d. between them is 500V. What is the magnitude of electric field, if it is uniform, in the region between them? Ans: 2500 V/m
2. An electron of mass [latex]9.1\times 10^{-31}[/latex] kg charge [latex]1.6\times 10^{-19}[/latex] C is situated in uniform electric field of intensity [latex]1.2\times 10^4\ Vm^{-1}[/latex]. Find the time it takes to travel 1 cm from rest. Ans: [latex]3.1\times 10^{-9}[/latex] s
3. Two charges [latex]+1\times 10^{-6}[/latex] C and [latex]-4\times 10^{-6}[/latex] C are separated by a distance of 2m. Determine the position of the null point. Ans: 2m outside from smaller one
4. A hollow spherical conductor of radius 12 cm is charged to [latex]6\times 10^{-6}[/latex] C. Find the electric field strength at the surface of sphere, inside the sphere at 8 cm and at distance 15 cm from the sphere. Ans: [latex]3.75\times 10^6\ NC^{-1}[/latex], 0, [latex]7.41\times 10^5\ NC^{-1}[/latex]
5. Two small spheres of charge [latex]+10\ \mu C[/latex] and [latex]+40\ \mu C[/latex] are placed 6 cm apart. Find the location of point between them where the field strength is zero. Ans: 0.02 m from [latex]+10\ \mu C[/latex]
6. Two charges [latex]-1\mu C[/latex] and [latex]+2\mu C[/latex] are placed at the corners A and B of an equilateral triangle ABC of side 2m. Calculate the electric field at C. Ans: 3897.11 N/C