Small Science information

ELECTRICITY

1) Charge is a fundamental particle in an account in an atom.It may be positive or negative.

2) Like charges repel each other.

3) Unlike charges attract each other.

     Coulomb(C):S.I.unit of charge

     1 Coulomb = Charge present an approx.6*10 to the power of 18 electrons

4) Charge on 1 electron = Negative charge of 1.6*10 per C

                                                     Q = ne

Where     Q = Charge(total)

                n = No. of electrons

                e = Charge on one electron

Current(I): the rate of flow of charge is called current.

                                    Current = Charge/Time

                                                  

                                            I = Q/T

S. I. unit of current = Ampere(A)

                                                 1 A=1 Cs per 1

                                             1 mA = 10 per 3 A

                                      1 micro A = 10 per 6 A

Current is measured by Ammeter. Its symbol is 

Ammeter has low resistances and always connected in series.

Direction of current is taken opposite to flow of electrons as electrons were not known at the time when the phenomenon of electricity was discovered first and current was considered to be flow of 

positive charge.

Potential difference (V): Work done to move a unit charge from one point to another.

1 Volt: When one joule is work done in carrying one coulomb charge then potential difference  is called one volt.

                                         V=W/Q

S. I. unit of potential difference = Volt(V)
                                       
Voltmeter: Instrument to measure potential difference.

            i)It high resistance and always connected in parallel. symbol is +(v)-

            ii)Cell is the simplest devise maintain potential difference.

           iii)current always flow from higher potential to lower potential.