static electricity (revised) - weebly static electricity happens when within a material are static...

Download Static Electricity (Revised) - Weebly Static electricity happens when within a material are static electric

Post on 16-Oct-2020

0 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • Chapter 15

    Static Electricity

  • At the end of this chapter, you should be able to

    � Show understanding that electrostatic charging by rubbing involves a transfer of electrons.

    � State that there are positive and negatives charges and that charge is measured in coulombs.

    � State that unlike charges attract and like charges repel.

  • At the end of this chapter, you should be able to

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

    � Draw the field of an isolated point charge and show understanding that the direction of the field lines gives the direction of the force acting on a positive charge.

    � Describe experiments to show electrostatic charging by conduction.

  • Quiz Time

    Use a piece of tissue paper to rub a plastic ruler. Place the rubbed side of the plastic ruler near your friend’s hair. What do you observe and why did it happen?

    A few strands of hair are attracted to the rubbed surface of the ruler. This is caused by electrostatics.

  • 15.1 Laws of Electrostatics

    � Electrostatics is the study of

    � Static electricity happens when

    within a material are

    static electric charges or electric charges at rest.

    positive charges and negative charges not equal.

  • Structure of an Atom

    � The atoms of all substances contain both positively-charged particles and negatively-charged particles.

    ––

    ++

    +

    +

    electron

    proton

    neutrons

    nucleus

    nucleus

    orbits of

    electrons

  • Structure of an Atom

    � All matter are made of invisible particles

    called

    ––

    ++

    +

    +

    electron

    proton

    neutrons

    nucleus

    nucleus

    orbits of

    electrons

    atoms. (Can be seen using an electron microscope.)

  • Structure of an Atom

    � Each atom has negatively-charged orbiting round a

    massive which consists of positively-charged particles called and neutral particles called

    - electron

    - proton

    - neutron

    electrons nucleus

    protons neutrons

  • Structure of an Atom

    � An atom is electrically balanced (uncharged) when the amount of protons is to the amount of electrons.

    + ++ −− −

    A substance that is uncharged.

    equal

  • Structure of an Atom

    � Atom is positively-charged when the amount of protons is the amount of electrons.

    + ++ −−

    A substance that is positively-charged.

    +

    more than

  • Structure of an Atom

    � Atom is negatively-charged when the amount of protons is the amount of electrons.

    + + −−

    A substance that is negatively-charged.

    − −

    less than

  • Measurement of electric charges.

    � Electric charges are measured in ( )coulomb C

    Q = I × t

    where Q is electric charges (C)

    I is electric current (A)

    t is time (s)

  • Measurement of electric charges.

    � The electric charge for one electron or proton is 1.6 x 10-19 C

  • 15.2 Electric Field

    � An electric field

    � The direction of the field is defined as

    is a region where an electric charge experiences an electric force.

    the direction of the force on a small positive charge.

  • 15.2 Electric Field

    +

  • 15.2 Electric Field

    -

  • 15.2 Electric Field

    � The strength of the field is indicated by

    The closer the field lines, the is the electric field in that region.

    � The strength of the field is

    how close the field lines are to each other.

    stronger nearer the charge and decreases further away from the charge.

    stronger

  • 15.2 Electric Field

    -+

  • 15.2 Electric Field

    ++

  • 15.2 Electric Field

    -

    + + + + + + +

  • 15.2 Electric Field

    + +

    + +

    + +

    +

    l l

    l l

    l l

    l

    l l

    l l

    + +

    + +

  • 15.3 Laws of Electrostatics

    � A material can be charged by

    � Static electricity occurs when two different materials are

    against each other. insulating

    rubbed

    friction.

  • 15.3 Laws of Electrostatics

    � During charging, are transferred from one material to another material

    electrons

  • +

    +

    +

    -

    --

    + + +

    + -

    -

    - -

    15.3 Laws of Electrostatics

    � A material become positively- charged when some electrons are

    -

    --

    wool

    polythene Wool becomes

    positively-charged

    lost by the material.

  • +

    +

    +

    -

    --

    + + +

    + -

    -

    - -

    15.3 Laws of Electrostatics

    � A material become negatively- charged when some electrons are

    -

    --

    wool

    polythene Polythene becomes

    negatively-charged

    gained by the material.

  • 15.3 Laws of Electrostatics

    � Charges are in the friction process, it

    is only

    (Similar to Energy)

    neither created nor destroyed

    transferred from one place to another.

  • Quiz Time

    Rub a balloon on a woolen sweater. Then place it near some bits of paper. Observe what has happen?

    The paper will be attracted to the balloon.

  • Quiz Time

    Run another balloon on a woolen sweater and placed it near to the balloon that was previously rubbed with the woolen sweater. Observe has happen?

    The balloons will repel one another.

  • From what we have learned so far, we can conclude that:

    � Only two charges (positive and negative) exist.

    � Friction produces 2 different kinds of charges on different materials.

    � Positively-charged material gives away electrons while negatively- charged material takes in electron.

    � Unlike charges attract while like charges repel.

Recommended

View more >