Electric Current

Streetlights, television, entertainment, applliances at home and at work - all these are powered by electricity. Electricity is very important nowadays. Everyday, everywhere, everytime, in everything - we need electricity. In this page we will discover how electricity is produced.

An atom will become an ion (charged atom) through different processes like rubbing, charging by contact, and induction. These charged particles will then move from one place to another in a material called conductor - a material which allows charged particles to pass through it. This flow of charges is called electric current.

Electric current is defined as the amount of charge that pass through a conductor per unit of time. It is expressed mathematically as,

\(I=\frac Qt\)


\(I=\text{electric current (Amperes, A)}\\ Q=\text{total charge (Coulombs, C)}\\ t=\text{time (seconds, s)}\)

The unit for electric current is named after the French physicist André Marie Ampère.

Example 1.

A rice cooker can cook 3 cups of rice in 10 mins with 950 C of charge. Calculate the amount of electric current during this time.


\(Q=950 \;C\\ t=10 \;mins\times \frac{60\;s}{min}=600\;s \)


\(I=\frac Qt\\ \;\,=\frac {950\;C}{600\;s}\\ \;\,=1.6\;A\)

It takes 1.6 A of current to cook the rice in 10 mins at 950 C of charge.

Example 2.

A fluorescent lamp has a current of 0.9 A. If it light up for \(1.5\times 10^3 \;s\), how much charge pass through its filament?


\(I=0.9\;A\\ t=1.5\times10^3\;s\)


\(Q=It\\ \;\;\,=(0.9\;A)(1.5\times 10^3\;s)\\ \;\;\,=1.35\times 10^3\;C\)

The charge that pass through the filament of the fluorescent lamp is \(1.35\times10^3\;s\).

Example 3.

How long will it take for an alectric waffle maker to make 5 waffles if it takes700 C of charge in 10 A of current?


\(I=10\;A\\ Q=700\;C\)


\(t=\frac QI\\ \;=\frac {700\;C}{10\;A}\\ \;=70\;s\)

If an electric waffle maker takes 700 C of charge in 10 A of current, it can cook 5 waffles in 70 seconds.