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© Boardworks Ltd 2003 IGCSE Electricity – Charge Aims: Describe simple experiments using electrostatic charges State that there are positive and negative.

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Presentation on theme: "© Boardworks Ltd 2003 IGCSE Electricity – Charge Aims: Describe simple experiments using electrostatic charges State that there are positive and negative."— Presentation transcript:

1 © Boardworks Ltd 2003 IGCSE Electricity – Charge Aims: Describe simple experiments using electrostatic charges State that there are positive and negative charges State that unlike charges attract and that like charges repel State that charge is measured in coulombs Describe charging by induction Recall and use the simple electron model to distinguish between conductors and insulators and give examples.

2 © Boardworks Ltd 2003 Charge ParticleCharge Proton Neutron Electron +1 none

3 © Boardworks Ltd 2003 Charge, attraction and repulsion

4 © Boardworks Ltd 2003 Attraction and repulsion Positive and positive________ Negative and negative________ Positive and negative________ repel attract Like charges repel, unlike charges attract.

5 © Boardworks Ltd 2003 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.

6 © Boardworks Ltd 2003 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?

7 © Boardworks Ltd 2003

8 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.

9 © Boardworks Ltd 2003 Experiment 1 Charge up one of the plastic strips Check the charge using the charge measuring device and the data logger Was the charge positive or negative Can you explain what has happened (use the word electrons)

10 © Boardworks Ltd 2003 Experiment 2 Charge up the same rod as in experiment 1 and attach it to the cradle Now charge up another rod and bring it close to the first What happens? What charge is on the new rod? Check with the charge measuring device

11 © Boardworks Ltd 2003 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

12 © Boardworks Ltd 2003 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

13 © Boardworks Ltd 2003 Experiment 3 Charge up a rod and bring it near to some small pieces of paper Try holding your rod near a stream of water from a tap Rub a balloon on your sweater (or hair) place it gently against the wall Can you explain what happens

14 © Boardworks Ltd 2003 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.

15 © Boardworks Ltd 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

16 © Boardworks Ltd 2003 Conductors and Insulators In all of the examples which particles move? Protons do not move in materials (they are trapped away in the nucleus) A good conductor has lots of electrons that are free to move – Free electrons An insulator does not have free electrons.

17 © Boardworks Ltd 2003 To do P171&173 Answer all questions

18 © Boardworks Ltd 2003 What is the charge on an electron? A.Positive B.Negative C.Neutral D.Depends upon the atom

19 © Boardworks Ltd 2003 What force can be used to charge insulators? A.Gravity B.Friction C.Weight D.Energy

20 © Boardworks Ltd 2003 If a current of 6A is run through a device for 6 seconds. What charge is delivered to the device? A.1A B.36A C.1C D.36C

21 © Boardworks Ltd 2003 If a kettle has a 13A current and is on for 2 minutes, what charge is delivered to the kettle? A.26 C B.6.5 C C.1560 C D.0.23 C

22 © Boardworks Ltd 2003 If 6C of charge is delivered at a potential difference of 5V, how much energy is delivered? A.1.2 J B.11 J C.30 J D.30 kJ

23 © Boardworks Ltd 2003 Core Describe simple experiments to show the production and detection of electrostatic charges State that there are positive and negative charges State that unlike charges attract and that like charges repel Distinguish between electrical conductors and insulators and give typical examples

24 © Boardworks Ltd 2003 Supplement State that charge is measured in coulombs Give an account of charging by induction Recall and use the simple electron model to distinguish between conductors and insulators


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