• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
5.2 - Internal Resistance, Power & Combining Resistors
 

5.2 - Internal Resistance, Power & Combining Resistors

on

  • 2,121 views

Electricity

Electricity

Statistics

Views

Total Views
2,121
Views on SlideShare
1,896
Embed Views
225

Actions

Likes
0
Downloads
29
Comments
0

2 Embeds 225

http://moodle.wortech.ac.uk 218
http://jujo00obo2o234ungd3t8qjfcjrs3o6k-a-sites-opensocial.googleusercontent.com 7

Accessibility

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    5.2 - Internal Resistance, Power & Combining Resistors 5.2 - Internal Resistance, Power & Combining Resistors Presentation Transcript

    • 5.2 - Internal Resistance, Electrical Power, Resistors in Series & Parallel 1
    • Internal ResistanceAll cells are made of materials that haveresistance, this is called InternalResistance (r)If the cell is connected to an ExternalResistor (R) then some of the energy isconverted from electrical energy to heatenergy inside the cell.The PD available for the circuit is EMF (E)therefore less than the EMF of thecell.This picture shows that some ofthe EMF is lost before the chargeseven leave the battery. PD (V) 2
    • Internal Resistance (cont) IUsing Ohms Law: E= Ir + IR I For the main Resistance in the circuit: V=IR Missing volts: Ir 3
    • More Internal ResistanceIf you connected a wire directly from one end of the Ibattery to the other then the Resistance (R) wouldbe very small.The Current (I) that flows would be enormous. IThis would cause loads of heat to be wasted by thecurrent as it moves through the Internal Resistanceof the battery.The battery would get very hot and run out ofenergy very fast. This is called a short circuit.Try it with the PhET Circuit Construction Kit:http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc or click on the pictureOR connect some steel wool across a battery. 4
    • Electrical Power (P)Power means the energy per second (Watts or Js-1)Remember some definitions:By substitution: 5
    • More Electrical Power Equations (P) Using: and Ohms Law: We can find the Power DISSIPATED (converted to heat) by a resistor. By substituting from Ohms Law: V=RI OR I=V/R 6
    • Combining Resistors1. Series Circuits Putting two resistors together is like putting two separate flights of stairs one after the other. The stairs are harder to climb 7
    • Combining Resistors2. Parallel CircuitsBecause there are more ways of getting round the circuit this is likemaking the stairs wider. The Resistance is less. 8
    • See how combinations of Resistors work: http://www.walter-fendt.de/ph14e/combrlc.htm or click on the picture Add Resistors and then highlight areas of the circuit to see the total resistance. Impedance is another word that can be used for Resistance 9