If you rapidly comb your dry hair, on a dry day , the comb and the hair will develop opposite charges. The comb will be able to pick up small pieces of paper. A table showing electrical measurements.
There are several methods to get an electric charge. The clouds develop very high charges. Cars often get charged by the contact of rubber tyres on the asphalt road surface. When you comb your hair the comb can also get charged. Click static electricity.
An A C If a 2 A current passed for 5 seconds the total charge passed will be = 2 x 5 = 10 C. ( Symbol for current is ‘I’ or ‘i’. while the symbol for ampere is ‘A’. As an equation:- Quantity= current x time. That is :- Coulombs = amperes x seconds.
The electric field is the force exerted on a unit positive charge. ( That is for 1 Coulomb) Arrows above the symbols show that the quantities are vectors. ‘ E’ without a sign would mean energy. Some times only a short line is used for this purpose.
Fig.3.The direction of the electric field is the same as the direction of force. Corollaries:-
Fig.4. Voltage measures the work done on a single coulomb. This is the same as V= J/q which is J = V x q. But q= I x t . Fig.5.Then substituting the value of q we get J = Vit.
Fig. 6. Work done in volts is equal to the product of Electric force and distance moved. For the charge to move, work has to be done. But Work = Force x
distance. Work , V = F Fig. 7. Substituting the value of F, which is E. q. we get :- W = E q d.
In order to convert Work into Volts we have to divide by the no. of charges. That is ‘q’. Volts is work done per charge. That means we have to divide by ‘q’.
Fig. 8. To find the work for a unit charge above value has to be divided by the quantity moved.
V = E ‘ Example 1. Find the missing values.
## Power is the rate of using energy.As electrical energy in Joules = Volt x Current . X time. To find the rate of using energy it has to be divided by time.
2.1 The maximum electrical energy it can supply.1. V= ir so r = v/i……. r= 12/ 300 …….= 0.04 Ω 2. E=Vit ………. J = 12x 300 x30 …. E = 3600…...E = 108000 J 3. P - Vxi. ……..P= 12 x 300 ………...3600 W same as 3.6 kW. |

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