Electricity

Electric Current and Electric Circuit

Electric Current: The flow of electric charge is known as electric current. Electric current is carried by moving electrons through a conductor.
By convention, electric current flows in opposite direction to the movement of electrons.
Electric circuit: Electric circuit is a continuous and closed path of electric current.
Expression of Electric Current:- Electric current is denoted by letter ‘I’. Electric current is expressed by the rate of flow of electric charges. Rate of flow means the amount of charge flowing through a particular area in unit time.
If a net electric charge (Q) flows through a cross section of conductor in time t,
Therefore,
Where,I is electric current,Q is net charge and t is time in second.

SI unit:

SI unit of electric charge is coulomb (C).
One coulomb is nearly equal to 6 x 10¹⁸ electrons.
SI unit of electric current is ampere (A).
Ampere is the flow of electric charges through a surface at the rate of one coulomb per second.
This means if 1 coulomb of electric charge flows through a cross section for 1 second, it would be equal to 1 ampere.
Small quantity of Electric Current: Small quantity of electric current is expressed in milliampere and microampere. Milliampere is written as mA and microampere as μA
1mA (milliampere)= 10^-3A
1μA(microampere)=10^-6A
Ammeter: An apparatus to measure electric current in a circuit.

Example: 1 :– Find the amount of electric charge flowing through the circuit if an electric current of 5 A is drawn by an electric appliance for 5 minute.

Solution:
Given,
Electric current (I) = 5 A
Time (t) = 5 minute = 5 X 60 = 300 s
Electric charge (Q) =?
Therefore,
Q = 5 A x 300 s = 1500 C Answer

Example: 2 :– If a current of 2 ampere is drawn for 1 hour through the filament of a bulb, find the amount of electric charge flowing through the circuit.

Solution:
Given,
Electric current (I) = 2 A
Time (t) = 1 hour = 1 x 60 x 60 s = 3600 s
Electric charge (Q) =?
We know that Q = I x t
Therefore, Q = 2 A x 3600 s = 7200 C Answer

Example: 3 – In how much time 6000 coulomb of electric charge will flow, if an electric current of 10 A is drawn through an electric motor?

Solution:
Given,
Electric charge (Q) = 6000 C
Electric current (I) = 10 A
Time (t) = ?

Example: 4 – If an electric charge of 900 C flows through an electric bulb for half an hour, find the electric current drawn by the filament.

Solution:
Given, Electric charge (Q) = 900 C
Time (t) = Half an hour = 30 m = 30 x 60 = 1800 s
Electric current (I) =?

Example: 5 – If an electric charge of 15000 C flows through an electric iron for 5 minute, find the electric current drawn by filament of electric iron.

Solution:
Given, Electric charge (Q) = 1500 C
Time (t) = 5m = 5 x 60 = 300 s
Electric current (I) =?