Electricity electric current and circuit class ten science NCERT

# Electricity

## Electric Current & 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.

Fig: Conventional Flow of Electric Charge

If a net electric charge (Q) flows through a cross section of conductor in time t, then;

text(Electric Current) (I)=(text(Net charge) (Q))/(text(Time) (t))

Or, I=Q/t

Where,I is electric current,Q is net charge and t is time in second.

SI unit of Electric Charge and Current:

SI unit of electric charge is coulomb (C).

One coulomb is nearly equal to 6 xx 10^18 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.

Therefore; 1 A = (1 C)/(1 s)

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^(-3) A

1μA(microampere)=10^-6 A

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 xx 60 = 300 s

Electric charge (Q) =?

We know; I = Q/t

Or, Q = I xx t

Or, Q = 5 A xx 300 s = 1500 C

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 xx 60 xx 60 s = 3600 s

Electric charge (Q) =?

We know that Q = I xx t

Therefore, Q = 2 A xx 3600 s = 7200 C

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) = ?

We know; I = Q/t

Or, t = Q/I

Or, t = (6000 C)/(10 A) = 600 s

Or, t = 10 min

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 xx 60 = 1800 s

Electric current (I) =?

We know; I = Q/t

Or, I = (900 C)/ (1800 s) = 0.5 A

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 xx 60 = 300 s

Electric current (I) =?

We know; I = Q/t

Or, I = (1500 C)/(300 s) = 5 A