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
Q. An aircraft having awing span of 10 m flies at a speed of 720 kmph. If the vertical component of the earth's magnetic field is 3 X 10 -5 T, calculate the emf induced between th

A body of mass m1 , moving with velocity u1 collides head  on with a body of mass m2 moving with a velocity u2 the two bodies stick together after the collision the loss of kinetic

The Monkey and Zookeeper There is an attractive monkey down at the zoo. The monkey spends most of its day execution from a limb of a tree. The zookeeper feeds the monkey throug

Refractive index: The most important optical measurement for any transparent material is its refractive index (n). The refractive index is the ratio of the speed of light (c)


Illustrates some applications of holography? Applications of Holography Holography can be put to many of uses other than recording images. Holographic data storage is a proc

Steelyards Either Roman or Danish steelyards can be improvised using short lengths of lead or iron water pipe as counter-weights and loops of wire s pivots. The rod can be o

Einstein-Podolsky-Rosen effect; EPR effect: Assume the following quantum mechanical thought-experiment: Take a particle that is at rest and contain spin zero. It decays sponta

If the electrons striking the target eject an electron from the K-shell of the atom, a vacancy is crated in the K-shell. Instantly an electron from one of the outer most shell, say

C- Radiowave Heating( Diathermy) Short wave diathermy utilized electromagnetic wave in radio range ( ~10m ) and microwave range (~ 12cm) .Short wave diathermy penetrate deep into