# ELECTRIC CHARGES _ FIELDS -1

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ELECTRIC CHARGES & FIELDS

1. Five charges, each of value +q coulomb are placed on five vertices of a regular hexagon of side ‘a’ metres.
Find the magnitude of force on a charge –q coulomb placed at the centre of the hexagon.

2. Two identical charged spheres A&B repel each other with a force of 2.0 x 10 -5 N. A third identical but
uncharged sphere C is touched to A, and then placed at the mid-point between A and B. Calculate the net force
on C.

3. Two point charges +4e and +e are fixed a distance ‘a’ apart. Where a third point charge q should be placed on
the line joining the two charges so that it may be in equilibrium?

4. A pith ball A of mass 9 x 10 -5 kg carries a charge 5µC. What must be the magnitude and sign of the charge on
a pith-ball B held 2cm directly above the pith ball A, such that the pith-ball A remains stationary?

5. Four particles, each having a charge q, are placed on the vertices of a regular pentagon. The distance of each
corner from the centre is ‘a’. Determine the electric field at the centre of the pentagon.

6. An electric dipole, when held at 30° with respect to a uniform electric field of 104 N/C experiences a torque of
9x10 -26 Nm. Calculate dipole moment of the dipole.

7. A circular plane sheet of radius 10cm is placed in a uniform electric field of 5x105 N/C making an angle of 30°
with the field. Calculate electric flux through the sheet.

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ELECTRIC CHARGES & FIELDS

1. Five charges, each of value +q coulomb are placed on five vertices of a regular hexagon of side ‘a’ metres.
Find the magnitude of force on a charge –q coulomb placed at the centre of the hexagon.

2. Two identical charged spheres A&B repel each other with a force of 2.0 x 10 -5 N. A third identical but
uncharged sphere C is touched to A, and then placed at the mid-point between A and B. Calculate the net force
on C.

3. Two point charges +4e and +e are fixed a distance ‘a’ apart. Where a third point charge q should be placed on
the line joining the two charges so that it may be in equilibrium?

4. A pith ball A of mass 9 x 10 -5 kg carries a charge 5µC. What must be the magnitude and sign of the charge on
a pith-ball B held 2cm directly above the pith ball A, such that the pith-ball A remains stationary?

5. Four particles, each having a charge q, are placed on the vertices of a regular pentagon. The distance of each
corner from the centre is ‘a’. Determine the electric field at the centre of the pentagon.

6. An electric dipole, when held at 30° with respect to a uniform electric field of 104 N/C experiences a torque of
9x10 -26 Nm. Calculate dipole moment of the dipole.

7. A circular plane sheet of radius 10cm is placed in a uniform electric field of 5x105 N/C making an angle of 30°
with the field. Calculate electric flux through the sheet.

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