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KS4 Static electricity

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Charge

Particle Charge

Proton

Neutron

Electron

+1

none

-1

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Charge, attraction and repulsion

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Attraction and repulsion

Positive and positive ________

Negative and negative ________

Positive and negative ________

repel

repel

attract

Like charges repel, unlike charges attract.

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Charging objects

What do we call the force you get when two materials rub together?

Friction

Let’s say you rub an insulator with a cloth, two things can happen:

A. Electrons move from the cloth to the insulator.

B. Electrons move from the insulator to the cloth.

Let’s look at the two cases in more detail.

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Electrons move from the insulator to the cloth

Electrons move from the insulator to the cloth.

The cloth becomes negatively charged.

The insulator becomes positively charged.

It is only the electrons that are free to move.

What charge has the cloth?

What charge has the insulator?

+ ++ +

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Electrons move from the cloth to the insulator

Electrons move from the cloth to the insulator.

The cloth becomes positively charged.

The insulator becomes negatively charged.

What charge has the cloth?

What charge has the insulator?

It is only the electrons that are free to move.

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Identifying an unknown charge

If you have a rod with an unknown charge you can identify the charge using two methods.

If you bring it near a positively charged rod and it is attracted to the rod then the unknown

charge must be ________.

If you bring it near a positively charged rod and it is repelled by the rod then the unknown

charge must be _________.

negative

positive OR

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Identifying an unknown charge

If the rod is a negative rod then……..

If you bring it near a negatively charged rod and it is attracted to the rod then the unknown

charge must be ________.

If you bring it near a negatively charged rod and it is repelled by the rod then the unknown

charge must be _________.

positive

negative

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Inducing a temporary charge

+ - + - + -

+ - + - + -

+ - + - + -

If you bring a negatively charged rod near a piece of paper, why does the paper stick to the rod?

The paper has no charge!

As the rod approaches the paper, the electrons in the paper are repelled away from the rod.

This makes one side of the paper negative and one side positive, a charge has been induced on the paper and the positive side of the paper is attracted to the negative rod.

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+ - + - + -

+ - + - + -

+ - + - + -

If you bring a positively charged rod near a piece of paper, why does the paper stick to the rod?

The paper has no charge!

As the rod approaches the paper, the electrons in the paper are attracted towards the rod.

This makes one side of the paper negative and one side positive, a charge has been induced on the paper and the negative side of the paper is attracted to the positive rod.

Inducing a temporary charge

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What is the charge on an electron?

A. Positive

B. Negative

C. Neutral

D. Depends upon the atom

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What force can be used to charge insulators?

A. Gravity

B. Friction

C. Weight

D. Energy