Practical 9 - Determination of the internal resistance of a cell

Question 1

Equation for determining internal resistance

Answer 1

V = E - Ir

Question 2

Draw and label the circuit needed for this practical

Answer 2

(See notes)

Question 3

What acts as our external resistance?

Answer 3

The variable resistor

Question 4

What do cells have?

Answer 4

Their own internal resistance

Question 5

What happens to pd as the current runs? Why?

Answer 5

It drops as work is done by the battery against frictional forces - lost volts

Question 6

What do we measure in this practical?

Answer 6

Varied voltage and current readings at different resistances

Question 7

What type of graph do we plot?

Answer 7

V (y - axis) v.s I (x-axis)

Question 8

What type of graph will the current-voltage graph be?

Answer 8

Straight line

Question 9

What does the intercept on the y-axis represent?

Answer 9

Emf

Question 10

What does our gradient represent?

Answer 10

-r

Question 11

What are equal when a switch is open in the circuit?

Answer 11

V = ε

Question 12

When does V = ε?

Answer 12

When the switch is open

Question 13

What does ε equal when a switch is closed? What does this equation lead to?

Answer 13

ε = V + Vl
ε = IR + Ir
V = IR = ε - Ir