1.What is electricity ?
Ans : Electricity is a general term used for all phenomena caused by electric charge whether static or in motion.
Ans : There are two types,(1) static Electricity and (2) Current Electricity.
Ans : Static electricity means electricity at rest in contradistinction to dynamic or current electricity the effects of which are purely due to the electrostatic field produced by the charge. As it is obtained by rubbing two substance such as glass and silk it is also called frictional electricity.
Ans : Current electricity means the electricity in motion the effects of which are due to the flow of electrons in a conductor.
Ans : There are two types :- (1) Direct current and (2) Alternating current.
Ans : The methods are –
i) By means of frictions- Static electricity is produced.
ii) By means of chemical action in cells and batteries.
iii) By means of mechanical driving- Generator produces electricity in two dissimilar methods.
iv) By means of heat – Thermal electricity is produced.
v) By means of lighting effect – Electricity is produced in photo electric cell.
Ans : (1)Battery, (2) Generator and (3) Thermocouple.
Ans : Heating, Lighting, Welding, Running of Motors, Battery charging, Electroplating, Relays, telephones, Electronic Equipment, etc.
Ans : (1) Physiological effect (Electric shock), (2)Heating effect (Lamp, Heater, Fuse), (3)Magnetic effect (Fan, Motor, Electric bell), (4) Chemical effect (Battery charging and Electroplating) and (5) X – Ray effect ( X- Rays).
Ans : A.C is the abbreviation of an alternating current which flows to and from in a circuit in alternate direction periodically with the variation of its magnitude in regular manner that after reaching a maximum in one direction decreases to zero, finally reversing and reaching a maximum in the opposite direction decreases to zero again the cycle of pulsation being repeated continuously. D.C. is the abbreviation of a direct current which flows in one direction only and which does not have any appreciable pulsation in its magnitude.
Ans : (1) Battery charging, (2)Electroplating, (3)Electrolysis, (4) Relays, (5) traction motors, (6) Cinema projector.
Ans : (1) House hold appliances, (2) Fan, (3) Refrigerators, (4)Power driving motors. (5)Radio and T.V. Set etc.
Ans : By seeing fan and tube light connection.
Ans : Conductors are those metallic substances which have a large number of free electrons and offer a little resistance to the flow of electricity through them.
Ans : Insulators are those nonmetallic substances which have comparatively very few free electrons and offer enormous resistance that they do not practically allow electricity to flow through them.
Ans : Copper, Aluminum, Brass, Iron, Phosphor Bronze, Silver, Zinc, Tungsten, Nickel, etc.
Ans : Mica, Oil impregnated paper, Vulcanized rubber, Glass, Bakelite, Porcelain, Varnished Cotton, Wood etc.
Ans : “Dielectric Strength”.
Ans : Dielectric strength is the maximum kilovolts per millimeter which an insulating medium can withstand without breakdown.
Ans : The dielectric strength depends on the following factors – i. Thickness of the specimen,
ii. Size and shape of electrodes used in applying stress,
iii. Form or distribution of the field of electric stress in the material,
iv. Frequency of the applied voltage,
v. Rate and duration of voltage application,
vi. Fatigue with repeated voltage application,
viii. Moisture content and
ix. Possible chemical changes under stress.