R Ch 34 Electric Current pg 1 - PowerPoint PPT Presentation

1 / 21
About This Presentation
Title:

R Ch 34 Electric Current pg 1

Description:

R Ch 34 Electric Current pg 1 Text Qs pg 545 RQ 1, 3-19,21 ,22 R 34.1 Flow of Charge pg 2 Charges flow in a conductor when there is a difference in voltage (another ... – PowerPoint PPT presentation

Number of Views:62
Avg rating:3.0/5.0
Slides: 22
Provided by: Wbe9
Learn more at: http://www.rlas-116.org
Category:
Tags: current | electric | volt

less

Transcript and Presenter's Notes

Title: R Ch 34 Electric Current pg 1


1
R Ch 34 Electric Current pg 1
  • Text Qs pg 545
  • RQ 1, 3-19,21 ,22

2
R 34.1 Flow of Charge pg 2
  • Charges flow in a conductor when there is a
    difference in voltage (another name for voltage
    is potential). The flow will continue until both
    locations have the same voltage

3
R 34.2 Electric Current pg 3
  • Electric current is the flow of electric charge.
  • Solids only electrons flow
  • Liquids electrons positive ions flow
  • Gasses electrons positive ions flow
  • The overall or net charge of a conductor is zero,
    as a new charge enters another charge leaves

4
R 34.3 Voltage Sources pg 4
  • Cells are what we call batteries. Cells convert
    chemical energy to electrical energy
  • Dry cell flashlight battery
  • Wet cell car battery
  • Two cells hooked together battery
  • Generators like the alternator in your car
    power plant convert mechanical energy to
    electrical energy

5
R 34.3 Voltage Sources pg 5
  • The electrons have potential energy leaving the
    negative terminal heading to the positive
    terminal.
  • The electrons feel pressure to move. This
    pressure is called the voltage or EMF
    (electromotive force)

6
R 34.3 Voltage Sources pg 6
  • At home the power company provides a 120 volts of
    potential difference or pressure between the two
    holes in the socket.
  • This means there is 120 Joules of energy given to
    each Coulomb of charge (6 e18 electrons)

7
R 34.3 Voltage Sources pg 7
8
R 34.4 Electrical Resistance pg 8
  • Electrical Resistance is a measure of how
    difficult it is for the electrons to flow through
    a wire depends on
  • 1) material type, different metal has diff.
    resistanc
  • 2) wire thickness, thicker wire less resistance
  • 3) length of wire, longer wire more resistance
  • 4) temperature, higher temp more resistance

9
R 34.5 Ohms Law pg 9
  • Ohms law is the V I x R

10
R 34.5 Ohms Law Electric Shock pg 10
  • Skin, shoes clothes all provide a good deal of
    resistance to current electricity. Dry skin has
    about 500,000 ohms of resistance.
  • If current travel through your body two things
    can happen
  • 1) overheating (cooking) tissue
  • 2) disrupt nerve function, stopping the heart
    or breathing

11
R 34.6 Ohms Law Electric Shock pg 11
  • To help someone who is being electrocuted
  • 1) think
  • 2) use an insulator (probably wood or plastic) to
    break contact between the body and the wire
  • Birds contact wires all the time but do not get
    shock because
  • 1) their scaly feet are good insulators
  • 2) both feet are on the same wire, there is no
    difference in voltage so no current flows from
    one foot to the other

12
R 34.7 Direct Current Alternating Current pg 12
  • Direct Current or DC current the charges only
    flow in one direction.
  • Alternating Current or AC the charges vibrate
    back forth and never move out of the wire

13
R 34.7 Direct Current Alternating Current pg 13
  • In North America the electron vibrates back and
    forth 60 times each second (due a change in
    voltage polarity) with a 120 volts of EPE
  • Europe uses a 220 volt system because it is more
    efficient.

14
R 34.7 Direct Current Alternating Current pg 14
  • The 60 vibrations a second is called 60 cycle or
    60 Hertz electricity.
  • It means that for 1 / 120th of a second the wire
    is positive and for the next 1 / 120th of a
    second the wire is negative.

15
R 34.7 Direct Current Alternating Current pg 15
  • At your house there is a circuit breaker box call
    the electric service drop.
  • A 120 volt negative wire and a 120 volt positive
    wire enter your house from the neighborhood
    electric line.
  • Normally these are kept separate but they can be
    combined to make 240 volts for the air
    conditioning etc.

16
R 34.8 Converting AC to DC pg 16
  • To convert the AC current that comes out of the
    wall socket to DC needed to run household devices
    requires three things
  • 1) a transformer, to lower or raise the voltage
  • 2) a diode a one-way valve to eliminate the
    vibration back and forth
  • 3) a capacitor to fill in the missing electrons

17
R 34.8 Converting AC to DC pg 17
18
R 34.9 The Speed of Electrons in a Circuit pg 18
  • DC current electrons moves about 0.01 cm/sec
    because the electrons keep bouncing off the
    positive nucleus which are in the way.
  • AC current electrons just vibrate back and forth
    and dont go anywhere
  • An electric field is what really moves through
    the wire at close to the speed of light

19
R 34.10 The Source of electrons in a Circuit pg
19
  • So the truth is electrons do not come out of a
    wire into a light bulb. An electric field comes
    out of the wire and pushes and or pulls on the
    electrons in light bulb.
  • The electric field caused the electrons to move
    and do work. Just like a magnet would push or
    pull a metal ball bearing.

20
R 34.10 The Source of electrons in a Circuit pg
20
  • When you get an electric shock what you feel is
    the electrons in your body being pushed pulled
    60 times each second with 120 Joules of EPE.

21
R 34.11 The Source of electrons in a Circuit pg
21
  • Electric power is the rate at which electric
    energy is converted to heat, light or mechanical
    energy.
  • The electric company sells you Kilowatt-hours of
    energy, (not Joules of energy)
  • So 10 100 watt light bulbs burning for one hour
    is 1 kw-hr of electric energy.
Write a Comment
User Comments (0)
About PowerShow.com