The concept of electricity was devised long before scientists had a clear understanding of how electricity worked at the atomic level. They defined an electric current as the flow of a positive charge from the positive terminal (anode) of a battery, or some other source of energy, to the negative terminal (cathode). As well all know now, current is actually the flow of electrons, which are negatively charged, and come from the negative terminal. This creates a very interesting situation. When we talk about the direction of the flow of an electric current, it is actually the opposite direction to the way in which the electrons are flowing. Keep this very strange dogma in mind, it may help you to understand what is going on in these electrical circuits.

So what do you actually mean by electric current? Well electric current is a measure of the amount of charge which pass through a point in any given instance of time. Basically, its how much electricity is going through the wires. Current is measured in Amperes (amps), and one amp is technically defined as one coulomb of charge passing a point in one second.

A charge of 10 coulombs has been travelling through the wire of a simple circuit, with a current of 3A. How long has the current been flowing for?

Answer :

This is how we work through the question, using the formula you have just learnt.

I = q/t

I = 3A q = 10C t = ?

3 = 10/t

t = 10/3

t = 3.34 (2 decimal places)

Congratulations!! You have just completed your first lesson in electrodynamics. You are now an expert on electric current. Its time for you to show us how much you have learnt from this lesson. Have a go at these 5 questions. When you’ve done that, you can go to your next lesson, an introduction to Ohm’s Law.

Questions:

1) Which of the following statements is true about current?

a) Current flows in the same direction as the electrons.
b) Current flows perpendicular to the flow of electrons.
c) Current flows in the opposite direction to the electrons.
d) Current does not flow in a circuit.

2) Which of the following is current measured in:

a) Volts.
b) Coulombs.
c) Ohms.
d) Amperes.

3) In chester's car, a particular metal conductor has 5 coulombs flowing though it in 3 seconds. What is the current in the conductor (in amps, correct to 3 decimal places)?

4) The current in wire is measured to be 3 amps, what charge has flowed through the wire after 1 minute (in coulombs)?

5) In a copper wire of current 7 amps, a charge of 84 coulomb has flowed through it. For how long has current been flowing (in seconds)?

Answers:

1) C
2) D
3) 1.667
4) 180
5) 12