chapter21--PHY131 JAB

chapter21--PHY131 JAB - 1 Chapter 21: Electric charge and...

Info iconThis preview shows pages 1–15. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 Chapter 21: Electric charge and electric field Electric charge Conductors & insulators Coulombs Law Electric field and electric forces Electric field calculations Electric field lines Electric dipoles 2 21.1 Electric Charge There are two kinds of electric charge: positive and negative. A body is electrically neutral if the sum of all the charges in a body is zero. Charge is a conserved quantity. What we call electric charge is a material property; it is not a substance. 3 The elementary unit of charge is e = 1.602 10-19 C. The charge on the electron is -1e. The charge on the proton is +1e. The charge on the neutron is 0e. Charge can move through matter. The charge of a body is quantized. 4 Experiments show that likes charges will repel each other and unlike charges will attract each other and that the force decreases with increasing distance between charges. 5 An object can become polarized if the charges within it can be separated. + + + + +----- This body is electrically neutral. By holding a charged rod near the body, it can be polarized. + + + + +----- + + + + + 6 + + + + + An uncharged ball hangs from a string. If a positively charged rod is brought near the ball what happens? Is the result the same or different if the rod is negatively charged? 7 Question: I hand you two objects, how can you determine if it has positive charge, negative charge, or is neutral? Question: Suppose there is a third type of charge. What test(s) would reveal if an object had this third type of charge? 8 21.2 Conductors, insulators and induced charges A conductor is made of material that allows electric charge to move through it easily. An insulator is made of material that does not allow electric charge to move through it easily. 9----- A conductor is placed next to an uncharged ball. What happens to the ball when a charged rod is brought into contact with the conductor? What about when an insulating rod replaces the conductor? 10 Conductors are easily polarized. These materials have free electrons which are able to move around inside the material. Any charges that are placed on a conductor will arrange themselves in a stable distribution. This stable situation is called electrostatic equilibrium. Properties of conductors 11 Example: Estimate the number of electrons in a typical human. Assume m = 75 kg and that the body is composed entirely of water. moles 4170 g/mole 18 g 10 75 person typical a in water of moles 3 = = ( ) molecules 10 5 . 2 mole molecules 10 . 6 mole 4170 person typical a in molecules water 27 23 = = 12 Example continued ( ) electrons 10 5 . 2 molecule electrons 10 molecules 10 5 . 2 person typical a in electrons 28 27 = = 13 Summary Properties of charge Properties of conductors/insulators Charge polarization 14 21.3 Coulombs Law 2 2 1 r q q k F = 2 2 9 /C Nm 10 99 . 8 = k The magnitude of the force between two point charges is:...
View Full Document

This note was uploaded on 04/29/2008 for the course PHY 131 taught by Professor Fuchs during the Fall '07 term at ASU.

Page1 / 58

chapter21--PHY131 JAB - 1 Chapter 21: Electric charge and...

This preview shows document pages 1 - 15. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online