EMF conservation of energy and internal resistance

Question 1

What is emf ?

Answer 1

Energy gained by each coulomb of charge flowing through the cell
Total amount of energy= total amount of energy used
Total emf= total pd across resistances

Question 2

What is internal resistance ?

Answer 2

When a cell is connected across a resistor it is sometimes found that the pd across the resistor is less than the EMF
This means that not all energy being supplied by the cell is used up flowing through the resistor
Some of the energy is used up by charge flowing through the cell the cell has some internal resistance

Question 3

How can we find the internal resistance ?

Answer 3

We could find the external pd or terminal pd the pd measured across the terminals of the power supply, or the pd across the external part of the circuit
V=E-Ir

Question 4

How do we find the terminal pd ?

Answer 4

Found by the emf given to the power supply minus any pd needed to overcome the internal resistance of the power supply

Question 5

What are the effects of internal resistance ?

Answer 5

I=E/R+r
The maximum current would flow when the external resistance is 0

Question 6

What happens when there’s a large current

Answer 6

Small internal resistance