Electricity

we will discuss all important topics ;Think life without “electricity” in this modern society. Is it possible to survive
without electrical energy in world of technology. Since we are science student, so it
is necessary to understand the basic concept behind the word “electricity”
Charge®(q)
It is a very small particles present in an atom it can be either negative (electron) or
positive (proton)
“Coulomb” is the SI unit of charge, represented by C.
Net charge (Q)–Total charge
IC Net charge is equivalent to the charge contained in nearly electrons 18 6´10
Q = ne (n is no: of electron)
If Q = 1C, –19 e = 1.6 ´ 10 C (negative charge on electron)
Q
e
n = =
1
–19 1.6 ´ 10
=
100
16 ´18 10 18 = 6.2 ´ 10
18 n = 6 ´ 10 electron
Current (I)
Rate of flow of net charge is called current. Denoted by (I)
Q
t
I = t is time
SI unit of current is “Ampere” rep. by A.
Ampere®Defined as one coulomb of charge following per second.
In an electric circuit the electric current flow in the opposite direction of the flow of
electron (–ve charge) conventionally. It flows from the +ve terminal of battery or
cell to –ve terminal.
Small quantity of current are expressed in
–3 mA (milli Ampere) = 10 A
–6 uA (micro Ampere) = 10 A
Ammeter– It is an instrument used to measure the electric current in a circuit.
It is always connected in series m a circuit
+ –
It is represented by the symbol –––––––– A ––––––– in an electric circuit. It has
low resistance.
Electric Circuit– It is a closed path along which an electric current flow.
A
+ –
+
–
Battery
(Having 3 cells)
Key
Ammeter
Bulb
The arrow shows the direction
of electric current in circuit.
In this circuit ammeter is
connected in series.
The electron can only flow when there is difference of electric pressure. For
example “water flowing through a tube” It is only possible when there high
pressure at one side and low at another side, then it will move from high pressure to
low pressure.
In case of electric current, the flow of charge is made possible due to chemical
action with in a cell that generates the potential difference across the terminals of
the cell.
8. Electric potential Difference– It is defined as the work done in carrying a unit
charge from one point to another between the two points of an electric circuits.
V =
W
Q
V – Potential Difference
W – Work
Q – Net Charge
SI unit of potential difference – Volts rep. by “V”