IGCSE Coordinated Science: Electric Charge

IGCSE Coordinated Science: Electric Charge

Electric Charge

1. Describe and interpret simple experiments to show the production and detection of electrostatic charges

Electrostatic Attraction can be reproduced and observed in a simple experiment:

1. Get a balloon.
2. Inflate it.
3. Rub the balloon quickly on any dry surface e.g. a carpet.
4. Go to the nearest faucet/ water tap.
5. Turn it on.
6. Place the balloon close to but not touching the running water.

What do you notice?

You should see that the water bends towards the balloon.

2. State that there are positive and negative charges.

When two insulating materials are rubbed together (in this case a carpet and the balloon), the friction causes electrons on one material to be rubbed off and left stranded on the other.

Normally, objects are neutrally charged, meaning that the atoms have an equal number of protons and electrons. However, when we rub two insulating materials together, what we end up is one material is left too much electrons, and as result becomes negatively charged due to more electrons than protons.

Conversely, the other object is left with more protons than electron (loses it). Hence, it becomes positively charged.

Due to the nature of water molecules, they are polar, meaning that their molecules have a positive and negative charged ends, much like a magnet. They are very weakly attracted to charged objects.

3. Describe an electric field as a region in which an electric charge experiences a force.

An electric field is created when an electrically charged object is placed near another charged or polar object, creating a force of electrostatic attraction between the two.

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In our experiment, the water bends towards the negatively charged balloon because:

• The positive pole of the water molecules are attracted to the negatively charged ions of the balloon. The positive pole of the water molecule aligns and rotates towards the balloon and is pulled towards it.

We also have to consider the fact that the water molecules have a negative pole as well, so shouldn’t it repel each other as well?

• The negative poles of the water molecule are repelled by the negatively charged ions of the balloon.

However, the water molecules still bend towards the stream. Much like a magnet, since the positive poles of the water molecules are closer to the balloon since they are attracted to it, the force of attraction between the positive ends is stronger than the repulsion between the negative ends.

4. State that unlike charges attract and that like charges repel

In essence, in the above experiment we can see that:

• Unlike (opposite) charges attract. ( + ) → ← ( – )
• Like (same) charges repel. ( – ) ← → ( – )
• A good analogy would be magnets. Think of magnets.

5. Distinguish between electrical conductors and insulators and give typical examples

Conductors are materials in which an electric current can flow freely. Examples include metals such as steel and copper. Metals have the property of being conductors of electric. They generally have a low resistance.

Conversely, insulators are materials in which an electric current cannot/will have a hard time flowing through. Examples include materials such as wood, plastic, and glass. You should notice that electric circuits are never built entirely from these materials. They generally have a high resistance.