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What is current
Electricity

YOU ARE LEARNING:

What Is Current?

What Is Current?

What Is Current?

Electric current is the rate of flow of charge. Current flowing through metals is a flow of negative electrons.

1

We talk about the "flow of charge" in an electric current. But what do you think it is that actually flows?

A) Protons B) Neutrons C) Electrons

2

When we talk about the "flow of charge" in an electric current...

actually the thing that flows is electrons.

What material do we normally use to lead the flow of charge, for example in a cable to a phone charger?

We normally use metals to lead the charge in electric currents because metals are great ____________.

1

So why are metals such great conductors of electric current?

It has to do with the particle structure in metal.

2

Metals have a lot of free _____________ that are easily able to move.

3

So this is ultimately what the "flow of charge" in an electric current means

It is the movement of electrons through metal.

1

Now, current and charge are not the same thing!

To find the current, you need to work out how much charge runs past a fixed point in a certain amount of time, for example per second.

2

A charge of 80 coulombs80 \space coulombs runs past the fixed point A in 2 seconds. How many coloumbs of charge run through point A per second?

3

Now you have worked out the current

The current is the amount of charge that runs past a fixed point per second. In this case that was 40 coulombs/second40 \space coulombs/second.

4

But! You don't use coloumbs/secondcoloumbs/second as the unit for current. Which unit do you think you use?

A) Newtons B) Ampere C) Joules

5

The unit you use for current is ampere (A)

1 A1 \space A is essentially the same as 1 coulomb of charge/second.

So you worked out the current like this: 80 C2 s=40 A\frac{80 \space C}{2 \space s} = 40 \space A. What is the formula for working out current?

Current is abbreviated by II, charge by QQ and time by tt. Which one is the correct abbreviated form for the current formula?

So current is the flow of charge per second. That means that current is the _________ of flow of charge.

A charge of 1,500 C1,500 \space C passes through a fixed point over the course of 30 seconds. What is the current in ampere?

1

Summary! When we talk about the "flow of charge" in an electric current...

the thing that is actually flowing is electrons.

2

Metals are especially good conductors of electrical current...

because the particle structure of metals includes a lot of free electrons that can easily move.

3

An electric current is actually the rate of flow of charge

We work it out per second: current=chargetimecurrent = \frac{charge}{time} or I=QtI=\frac{Q}{t}

4

The unit for current is ampere (A)

1 ampere is the same as 1 coulomb/second1 C/s1 \space C/s, but the unit we use is AA, not C/sC/s