Internal resistance of circuit, Physics

Internal Resistance of Circuit:

As mentioned earlier in the section on batteries, every source of electricity, such as a cell or generator has resistance to current flow called internal resistance.

  • Cells (and batteries): The internal resistance is mainly due to the resistance of the electrolyte. This varies considerably with temperature and concentration of the electrolyte.
  • Generators. Internal resistance is mainly the resistance of the wires which form the internal windings.
  • Electronic Power Supplies. Here the internal resistance is due to the resistance of components within the power supply.
  • 653_internal resistance.png 
    When the source forces electrons around a closed circuit they must pass through the internal resistance of the source, thus causing a drop in voltage within the source itself, i.e. the source has to do work to push current through itself. This loss of potential or 'voltage drop' may be referred to as lost volts, since they are not available in the external circuit, thus the terminal voltage is less than the emf by the value of the lost volts when current is drawn from the supply.

CLOSED CIRCUIT     

TERMINAL VOLTAGE  =  EMF - LOST VOLTS

Loss of potential only occurs when current flows from the source.  If therefore the external circuit is open, no current flows and the terminal voltage is equal to the emf.

OPEN CIRCUIT

TERMINAL VOLTAGE  =  EMF

The Size of the 'lost voltage' is determined by the internal resistance and the current flowing (Ir).  For a given emf the larger the external resistance, the smaller the current and the smaller the 'lost volts'.  Thus if the internal resistance is much smaller than the external resistance the 'lost volts' is very small and the terminal voltage is almost equal to the source emf. 

 

Posted Date: 9/13/2012 3:26:11 AM | Location : United States







Related Discussions:- Internal resistance of circuit, Assignment Help, Ask Question on Internal resistance of circuit, Get Answer, Expert's Help, Internal resistance of circuit Discussions

Write discussion on Internal resistance of circuit
Your posts are moderated
Related Questions
describe the construction and working of michelson interformeter?

Illustrate about laser beam welding in short. Laser beam welding: Laser beam welding (LBW) is a welding technique utilized to join multiple pieces of metal by the use of a l

What is diffraction of light? Illustrate a graph showing the variation of intensity with angle in a single slit diffraction experiment. Write single feature which distinguishes the

What kind of batteries are used in TL coachees. Briefly explain about each one of them? Ans. In TL coaches two kind of batteries are used. They are SMF and VRLA batteries.

An electric kettle has a resistance of30?. What current will ?ow when it is connected to a 240V supply? Find also the power rating of the kettle   A current of 5A ?ows i

Explain Shape of the earth? Shape and size of the earth. The shape of the earth is regarded as a sphere, but it is mainly an oblate spheroid like as egg being slightly flatter

find the angle between two vectors if thier resultant is equal to either of them

how much time is required to raise the temperature of the water from A family comes home from a long vacation with laundry to-do and showers to take. The water heater has been t

WHY WE USE DELAY LINE IN CRO WHAT HAPPENS IF WE NOT USE IT?

The mass of a proton and of an antiproton is 1.00728 u. Recall that the conversion of exactly 1 u into energy yields 931.5 MeV. a. Measure the mass used up when a proton and