A bulb connected to an electric cell

Electric Current 
Moving charge is called electric current. The rate of flow of charge is the amount of current,      
so     I = Q/t = ne/t
Where Q = ne, Here, n = number of electrons, e = charge of electrons = 1.6×10–¹⁹c

1C = Charge of 6.25 × 10¹⁸ electrons.

Unit of Electric Current :  The S.I. unit of current is Ampere.
Smallest currents are measured in milliamperes (mA) and microampere (µA)
1mA= 10–3 A
1µA = 10–6A

Instrument to Measure Current: An ammeter is an instrument used for Measuring Electrical Current

*    It must be connected in series in the circuit.
*    Positive side of ammeter must be connected nearest of the positive terminal of the battery (electric cell), and vice versa.

Ex.1    How many electrons constitute current of one micro ampere ?
Sol.    Given : Current, 1 = 1µA = 10^–6 A
          We know, Q = ne
          Where n is the number of electrons and e is the charg on 1 electron and e = 1.6 × 10^–19 C

Ex.2    A battery can supply a charge of 2.5 × 10³ C. If the current is drawn from the battery at a rate of 12.5 A. Calculate the time in which battery will get discharged ?
Sol.    Given : Charge, Q = 2.5 × 10³ C
          Current, I = 12.5 A

A Bulb connected to an electric cell

A Bulb Connected to an Electric Cell

Filament: In an electric bulb, there is a thin tiny wire inside the glass cover. This is called a filament.

Terminal: All types of electric cells have two terminals:

• a positive terminal
• a negative terminal

Wire :

• An electric wire is a conducting path in an electric circuit, through which current flows.
• It is usually made out of a metal that is a good conductor of electricity.

Electric Bulb and its Working:

• It consists of a thin wire that glows due to the passage of current. This is known as the filament.

• An electric circuit provides a closed path for the current to flow. The terminals of the bulb are connected by wires to the electric cell.
• Sometimes the bulb does not glow as the filament gets fused (breaks) due to overheating.