## Friday, May 8, 2009

### 1. E L E C T R O S T A T I C S .3M ANSWERS,

E L E C T R O S T A T I C S .3M ANSWERS
1. DEFINE A NON-POLAR MOLECULE.GIVE EXAMPLE.
A nonpolar molecule is one in which the centre of gravity of the positive charges (protons) coincide with the centre of gravity of the negative charges (electrons). Example: O2, N2, H2. The nonpolar molecules do not have a permanent dipole moment.
2. DEFINE POLAR MOLECULE,GIVE EXAMPLE.
A polar molecule is one in which the centre of gravity of the positive charges is separated from the centre of gravity of the negative charges by a finite distance. Examples : N2O, H2O, HCl, NH3. They have a permanent dipole moment.
3. DEFINE ELECTRIC POLARISATION.
The alignment of the dipole moments of the permanent or induced dipoles in the direction of applied electric field is called polarisation or electric polarisation.
4. STATE THE APPLICATIONS OF CAPACITORS
(i) They are used in the ignition system of automobile engines
to eliminate sparking.
(ii) They are used to reduce voltage fluctuations in power
supplies and to increase the efficiency of power transmission.
(iii) Capacitors are used to generate electromagnetic oscillations
and in tuning the radio circuits.
5. WHAT IS EFFECTIVE CAPACITANCE OF CAPACITORS CONNECTED IN SERIES AND PARALLEL?
When a number of capacitors are connected in series, the reciprocal of the effective capacitance is equal to the sum of reciprocal of the capacitance of the individual capacitors.
1/CS = 1/C1 + 1/C2 + 1/C3.
The effective capacitance of the capacitors connected in parallel is the sum of the capacitances of the individual capacitors. CP = C1 + C2 + C3
6. WHAT IS CORONA DISCHARGE OR ACTION OF POINTS?
The leakage of electric charges from the sharp points on the charged conductor is known as action of points or corona discharge.
This principle is made use of in the electrostatic machines for collecting
charges and in lightning arresters.