Electric Current
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Electric Current. What is an electric current?. To understand what an electric current is, we must first learn the structure of (1). What is an electric current?. atom.

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Electric Current

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Electric Current


What is an electric current?

To understand what an electric current is, we must first learn the structure of (1).

What is an electric current?


atom


Matter is made up of atoms. An atom consists of a (2) (+) and (3) (-). Sometimes electrons can escape from an atom and move freely with the conductor. These electrons are called (4) electrons.

free electrons

nucleus

atom

electrons


A piece of copper wire contains many free electrons. When the wire is not connected to a dry cell, the free electrons move in different directions.

free electrons moving in different directions

atoms in the copper wire


However, when the ends of the copper wire are connected to a dry cell, the free electrons move in the (5)direction. This flow of free electrons is called an electric current.

flow of free electrons


SUMMARY

The electric current in a metal wire is a flow of .

F(6)____

e (7)_____

Activity 8(c)


Measuring

electric

current


Ammeter

(安培計)


What is the unit

of electric current?


Ampere

(安培)

(A)

Milliampere

(mA)(毫安培)


We use an (8) to measure the size of an electric current. The unit of electric current is (9). The symbol of the unit is (10).

Small currents are measured in milliampere (mA).

Experiment 8.4

Do you know?

Do you know?

Do you know?

Activity 8(d)


1. atom

2. nucleus

3. electrons

4. free

5. same

6. free

7. electrons

8. ammeter

9. ampere

10. A

Answers:


Analogy of

electric circuit


The water pipe system


Water pump

Water pipe

Flow of water

Water turbine

Tap

Water

The water pipe system:


The electric circuit


dry cell

Connecting wire

Light bulb

Flow of free electrons

Switch

Free electrons

The electric circuit:


Analogy


Water

Water pipe

Water turbine

Tap

Water pump

Flow of water

Free electrons

Connecting wires

Light bulb

Switch

Dry cell

Flow of _____ _____

Analogy of electric circuitwith water pipe system


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