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MCQs

Q1

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
a.
[latex]1\ ms^{-1}[/latex]
b.
[latex]2\ ms^{-1}[/latex]
c.
[latex]0.5\ ms^{-1}[/latex]
d.
[latex]1.4\ ms^{-1}[/latex]
Show answer
Correct answer: (D)
Q2

The force between two charges in air is 10 N. On inserting dielectric, the force becomes 4 N. Then dielectric constant of medium is
a.
2.5
b.
0.5
c.
2
d.
4
Show answer
Correct answer: (A)
Q3

The energy per unit volume is given by
a.
[latex]\frac{E^2}{\epsilon_o}[/latex]
b.
[latex]\epsilon_oE^2[/latex]
c.
[latex]2\epsilon_oE^2[/latex]
d.
[latex]\frac{1}{2}\epsilon_oE^2[/latex]
Show answer
Correct answer: (B)
Q4

[latex]NC^{-1}[/latex] has the same unit as
a.
volt meter
b.
volt/meter
c.
Farad-m
d.
Farad/m
Show answer
Correct answer: (B)
Q5

Maximum value of electric intensity due to charged sphere is at
a.
center
b.
surface
c.
infinity
d.
half the radius of the sphere
Show answer
Correct answer: (B)
Q6

An electric dipole kept in uniform electric field. It experiences
a.
a force and a torque
b.
a force, but no torque
c.
a torque but no force
d.
neither a force nor a torque
Show answer
Correct answer: (C)
Q7

The electric field intensity at the surface of charged conductor is
a.
zero
b.
directed normally to the surface
c.
directed tangentially to the surface
d.
directed along [latex]45^o to the surface
Show answer
Correct answer: (B)
Q8

Electric intensity at a point varies as [latex]r^{-1}[/latex] for
a.
a point charge
b.
an electric dipole
c.
a plane infinite sheet of charge
d.
a line charge of infinite length
Show answer
Correct answer: (D)
Q9

If one penetrates a uniformly charged hollow sphere, the electric field strength E
a.
increases
b.
decreases
c.
remains same at the surface
d.
is zero at all points
Show answer
Correct answer: (D)
Q10

If electric field is uniform, the electric lines of forces are
a.
Divergent
b.
convergent
c.
Circular
d.
parallel
Show answer
Correct answer: (D)

Theoretical questions

Q1

Define electric field and electric field intensity.

Q2

Can two electric lines of force intersect each other? Explain.

Q3

What is the magnitude of an electric field which will balance the weight of an electron on the surface of earth?

Q4

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.

Q5

Under what conditions, the electric lines of force are curved?

Q6

A charge particle is free to move in an electric field. Will it always move along an electric lines of force?

Q7

When an iron plate is placed between two charges, what will be the electrostatic force of attraction between them?

Q8

An electron and a proton are placed in a uniform electric field; will their acceleration be same?

Q9

What will be the electric field strength at a point mid-way between two equal and opposite charges?

Q10

State gauss theorem. What is Gaussian surface?

Q11

Would Gauss law be helpful for determining the electric field of a dipole?

Q12

Why do the electrostatic field lines not form closed loops?

Q13

Draw lines of force to represent a uniform electric field.

LONG ANSWER QUESTION
Q14

State Gauss’s theorem in electrostatics. Use this theorem to calculate electric field due to a solid charged sphere at a point inside it.

Q15

State and explain Gauss’s theorem in electrostatics and use it to find the electric field intensity due to a hollow charged spherical conductor.

Q16

State and explain Gauss’s theorem in electrostatics. Use it to obtain an expression for electric field intensity due to a linearly charged body.

Q17

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

Q1

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

Q2

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

Q3

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

Q4

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]

Q5

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]

Q6

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