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# Unit 3 phy watch

1. Guys can u tell that what happens if there is an internal resistance in the cell?
2. (Original post by Aanika)
Guys can u tell that what happens if there is an internal resistance in the cell?
All cells have internal resistance in reality.

Your question is rather vague - do you have a specific problem to solve which will aid explanation?

In general, internal resistance has the effect of placing a series resistance between the cell producing the emf and the battery terminals connected to the load, so as to produce a potential divider action.

i.e. the battery terminal potential will be less than the open circuit cell emf when a load resistance is placed across the battery terminals.
3. Oh im sorry i should have been more specific...im studying IAL physics n this question is realted to physics unit2.I wanted to ask about the voltage drop that y does it happen if there is an internal resistance in the cell...?
4. (Original post by Aanika)
Oh im sorry i should have been more specific...im studying IAL physics n this question is realted to physics unit2.I wanted to ask about the voltage drop that y does it happen if there is an internal resistance in the cell...?
Think of it as a potential divider action:

I = Vin / (R1 + R2)

Vout = IR2

Vout = VinR2 / (R1 + R2)

i.e. The resistance R1 will cause a voltage drop such that Vout = Vin - VR1
Voltage potential is used up by R1.

Now replace Vin with the cell e.m.f. and R1 with the cell internal resistance (r) such that Vout becomes the battery terminals and the same thing happens.

There will be a voltage drop across the cell internal resistance and hence the battery terminal voltage will be less then the cell e.m.f. with the magnitude of the loss dependent on the load resistance R:

Vterminals = E r / (r + R)

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