In a certain region of space, electric field is along the z-direction throughout. The magnitude of electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 105 NC-1 per metre. What are the force and torque experienced by a system having a total dipole moment equal to 10-7 Cm in the negative z-direction?
Dipole moment of the system, p = q × dl = - 10 - 7 C m
Rate of increase of electric field per unit length,
Force (F) experienced by the system is given by the relation,
F = qE
= - 10 - 7 × 10 - 5
= - 10 - 2 N
The force is - 10 - 2 N in the negative z-direction i.e., opposite to the direction of electric field. Hence, the angle between electric field and dipole moment is 180°.
Torque (Ä) is given by the relation,
Ä = pE sin180°
= 0
Therefore, the torque experienced by the system is zero.
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(a) Estimate the number of electrons transferred (from which to which?)
(b) Is there a transfer of mass from wool to polythene?
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(a) What is the total capacitance of the combination?
(b) What is the potential difference across each capacitor if the combination is connected to a 120 V supply?
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(a) Inside the sphere
(b) Just outside the sphere
(c) At a point 18 cm from the centre of the sphere?
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