Electric Charges and Fields Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. A solid conducting sphere of radius a has a net
positive charge 2Q. A conducting spherical shell of
inner radius b and outer radius c is concentric with the
solid sphere and has a net charge – Q.The surface
charge density on the inner and outer surfaces of the
spherical shell will be respectively
(a)
(b)
(c)
(d)
Page 2


PART-I (Single Correct MCQs)
1. A solid conducting sphere of radius a has a net
positive charge 2Q. A conducting spherical shell of
inner radius b and outer radius c is concentric with the
solid sphere and has a net charge – Q.The surface
charge density on the inner and outer surfaces of the
spherical shell will be respectively
(a)
(b)
(c)
(d)
2. In the figure, the net electric flux through the
area A is  when the system is in air. On
immersing the system in water the net electric
flux through the area
(a) becomes zero
(b) remains same
(c) increases
(d) decreases
3. An electric dipole is placed in a uniform electric field. The dipole will
experience
(a) a force that will displace it in the direction of the field
(b) a force that will displace it in a direction opposite to the field.
(c) a torque which will rotate it without displacement
(d) a torque which will rotate it and a force that will displace it
4. Figure shows two charges of equal magnitude separated by a distance
2a. As we move away from the charge situated at x = 0 to the charge
situated at x = 2a, which of the following graphs shows the correct
behaviour of electric field ?
(a)
(b)
Page 3


PART-I (Single Correct MCQs)
1. A solid conducting sphere of radius a has a net
positive charge 2Q. A conducting spherical shell of
inner radius b and outer radius c is concentric with the
solid sphere and has a net charge – Q.The surface
charge density on the inner and outer surfaces of the
spherical shell will be respectively
(a)
(b)
(c)
(d)
2. In the figure, the net electric flux through the
area A is  when the system is in air. On
immersing the system in water the net electric
flux through the area
(a) becomes zero
(b) remains same
(c) increases
(d) decreases
3. An electric dipole is placed in a uniform electric field. The dipole will
experience
(a) a force that will displace it in the direction of the field
(b) a force that will displace it in a direction opposite to the field.
(c) a torque which will rotate it without displacement
(d) a torque which will rotate it and a force that will displace it
4. Figure shows two charges of equal magnitude separated by a distance
2a. As we move away from the charge situated at x = 0 to the charge
situated at x = 2a, which of the following graphs shows the correct
behaviour of electric field ?
(a)
(b)
(c)
(d)
5. An electric dipole is placed along the x-axis at the origin O. A point P is
at a distance of 20 cm from this origin such that OP makes an angle p/3
with the x-axis. If the electric field at P makes an angle ? with the x-
axis, the value of ? would be
(a)
(b)
(c)
(d)
6. A spherically symmetric charge distribution is characterised by a charge
density having the following variations:
 for r < R?(r) = 0 for r = R
Where r is the distance from the centre of the charge distribution ?
o
 is a
constant. The electric field at an internal point (r < R) is:
(a)
(b)
Page 4


PART-I (Single Correct MCQs)
1. A solid conducting sphere of radius a has a net
positive charge 2Q. A conducting spherical shell of
inner radius b and outer radius c is concentric with the
solid sphere and has a net charge – Q.The surface
charge density on the inner and outer surfaces of the
spherical shell will be respectively
(a)
(b)
(c)
(d)
2. In the figure, the net electric flux through the
area A is  when the system is in air. On
immersing the system in water the net electric
flux through the area
(a) becomes zero
(b) remains same
(c) increases
(d) decreases
3. An electric dipole is placed in a uniform electric field. The dipole will
experience
(a) a force that will displace it in the direction of the field
(b) a force that will displace it in a direction opposite to the field.
(c) a torque which will rotate it without displacement
(d) a torque which will rotate it and a force that will displace it
4. Figure shows two charges of equal magnitude separated by a distance
2a. As we move away from the charge situated at x = 0 to the charge
situated at x = 2a, which of the following graphs shows the correct
behaviour of electric field ?
(a)
(b)
(c)
(d)
5. An electric dipole is placed along the x-axis at the origin O. A point P is
at a distance of 20 cm from this origin such that OP makes an angle p/3
with the x-axis. If the electric field at P makes an angle ? with the x-
axis, the value of ? would be
(a)
(b)
(c)
(d)
6. A spherically symmetric charge distribution is characterised by a charge
density having the following variations:
 for r < R?(r) = 0 for r = R
Where r is the distance from the centre of the charge distribution ?
o
 is a
constant. The electric field at an internal point (r < R) is:
(a)
(b)
(c)
(d)
7. A charge q is placed at the centre of the open end of a
cylindrical vessel. The flux of the electric field through the
surface of the vessel is
(a) zero
(b)q/e
o
(c) q/2e
o
(d)2q/e
o
8. A short electric dipole of dipole moment  is placed at a distance r
from the centre of a solid metallic sphere of radius a (<< r) as shown in
the figure. The
electric field intensity at the centre of sphere C due to induced charge on the
sphere is
(a) zero
(b) along CO
(c) along OC
(d) along CO
9. A semi-circular arc of radius ‘a’ is charged uniformly and the charge
per unit length is ?. The electric field at the centre of this arc is
(a)
Page 5


PART-I (Single Correct MCQs)
1. A solid conducting sphere of radius a has a net
positive charge 2Q. A conducting spherical shell of
inner radius b and outer radius c is concentric with the
solid sphere and has a net charge – Q.The surface
charge density on the inner and outer surfaces of the
spherical shell will be respectively
(a)
(b)
(c)
(d)
2. In the figure, the net electric flux through the
area A is  when the system is in air. On
immersing the system in water the net electric
flux through the area
(a) becomes zero
(b) remains same
(c) increases
(d) decreases
3. An electric dipole is placed in a uniform electric field. The dipole will
experience
(a) a force that will displace it in the direction of the field
(b) a force that will displace it in a direction opposite to the field.
(c) a torque which will rotate it without displacement
(d) a torque which will rotate it and a force that will displace it
4. Figure shows two charges of equal magnitude separated by a distance
2a. As we move away from the charge situated at x = 0 to the charge
situated at x = 2a, which of the following graphs shows the correct
behaviour of electric field ?
(a)
(b)
(c)
(d)
5. An electric dipole is placed along the x-axis at the origin O. A point P is
at a distance of 20 cm from this origin such that OP makes an angle p/3
with the x-axis. If the electric field at P makes an angle ? with the x-
axis, the value of ? would be
(a)
(b)
(c)
(d)
6. A spherically symmetric charge distribution is characterised by a charge
density having the following variations:
 for r < R?(r) = 0 for r = R
Where r is the distance from the centre of the charge distribution ?
o
 is a
constant. The electric field at an internal point (r < R) is:
(a)
(b)
(c)
(d)
7. A charge q is placed at the centre of the open end of a
cylindrical vessel. The flux of the electric field through the
surface of the vessel is
(a) zero
(b)q/e
o
(c) q/2e
o
(d)2q/e
o
8. A short electric dipole of dipole moment  is placed at a distance r
from the centre of a solid metallic sphere of radius a (<< r) as shown in
the figure. The
electric field intensity at the centre of sphere C due to induced charge on the
sphere is
(a) zero
(b) along CO
(c) along OC
(d) along CO
9. A semi-circular arc of radius ‘a’ is charged uniformly and the charge
per unit length is ?. The electric field at the centre of this arc is
(a)
(b)
(c)
(d)
10. A hollow cylinder has a charge q coulomb
within it. If f is the electric flux in units of
voltmeter associated with the curved surface
B, the flux linked with the plane surface A in
units of voltmeter will be
(a)
(b)
(c)
(d)
11. A point Q lies on the perpendicular bisector of an electrical dipole of
dipole moment p. If the distance of Q from the dipole is r (much larger
than the size of the dipole), then the electric field at Q is proportional to
(a) p
–1
 and r
–2
(b)p and r
–2
(c) p
2
 and r
–3
(d)p and r
–3
12. The spatial distribution of electric field due to charges (A, B) is shown
in figure. Which one of the following statements is correct ?