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What Is Current?
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What Is Current?

lesson introduction

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

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2

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

actually the thing that flows is electrons.

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

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

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1

So why are metals such great conductors of electric current?

It has to do with the particle structure in metal.

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2

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

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3

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

It is the movement of electrons through metal.

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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.

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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?

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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.

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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

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5

The unit you use for current is ampere (A)

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

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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?

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

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

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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?

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1

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

the thing that is actually flowing is electrons.

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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.

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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}

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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

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