Resistance
Download
1 / 55

Resistance - PowerPoint PPT Presentation


  • 128 Views
  • Uploaded on

Resistance. Review of Resistors. The resis tance is a n intrinsic property of a material which impedes the flow of c harge requiring a pd to be applied so that there can be current flow. Review of Resistors.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Resistance' - winter


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Review of resistors
Review of Resistors

  • The resistance is an intrinsic property of a material which impedes the flow of charge requiring a pd to be applied so that there can be current flow.


Review of resistors1
Review of Resistors

  • The resistance is an intrinsic property of a material which impedes the flow of charge requiring a pd to be applied so that there can be current flow.

  • From ohm’s law, the resistance of a device is the ratio of the potential difference across it to the current flowing through it.




Rc circuits1
RC Circuits

  • The current in the previous circuits are time independent once the emf of the source is time independent.


Rc circuits2
RC Circuits

  • The current in the previous circuits are time independent once the emf of the source is time independent.

  • However we may have circuits which are time dependent.

  • An example is an RC circuit.





  • Consider charging: discharging of the capacitor through the resistor.

  • Initially the capacitor is uncharged.


  • Consider charging: discharging of the capacitor through the resistor.

  • Initially the capacitor is uncharged.

  • When in the charging position current flows and the capacitor charges.

  • From Kirchoff’s law:




  • Which can be written as: discharging of the capacitor through the resistor.

  • Since

  • We can rewrite the equation as,

  • Doing some algebra,


  • Which can be written as: discharging of the capacitor through the resistor.

  • Since

  • We can rewrite the equation as,

  • Doing some algebra,

  • We must separate the variables so that we can integrate and find the final charge on the capacitor.







q(t) discharging of the capacitor through the resistor.

VbatC

t

  • Taking the antilog and simplifying we get,



V constant.c

Vbat

t

  • The pd across the capacitor

  • Which gives


I(t)

Vbat/R

t




  • Since constant.

  • We can write that


  • Since constant.

  • We can write that

  • Separating variables,


  • Since constant.

  • We can write that

  • Separating variables,

  • Which in separated form is,



  • Integrating, constant.

  • We get

  • Which after simplification is,




q

CVbat

t


t the initial charge is CV

I(t)

Vbat

t


Power energy

Power, Energy the initial charge is CV


Power
Power the initial charge is CV

  • The net rate of energy transfer from the source (battery) P is given by,

  • Power is in watts(W) or joules/second

  • The rate at which energy is dissipated through through the resistor is,

  • The energy lost is in the form of thermal energy.

  • The power supplied to the capacitor is,


Energy
Energy the initial charge is CV

  • The total energy supplied by the battery in a time t is given by,

  • The total energy dissipated in a time t,

  • The total energy supplied to the capacitor in time t,


Energy1
Energy the initial charge is CV

  • From the conservation of energy,


Resistance in series and parallel

Resistance in Series and Parallel the initial charge is CV















ad