Circuit Calculations

Question 1

what is the formula for current passing through the cell?

Answer 1

current = emf / total circuit resistance

Question 2

What is the formula for pd across each resistor in series with the cell?

Answer 2

• p.d. across each resistor = current x resistance of each resistor

Question 3

What is the total internal resistance of a circuits with cells in series?

Answer 3

• Total internal resistance is the sum of individual internal resistances.
• This is because cells, and therefore internal resistances are in series.

Question 4

What is the formula for current for cells in series?

Answer 4

For circuit with n identical cells in parallel, current through each circuit =
I / n
I = total current provided by cells.
n = total number of cells.

Question 5

What is the formula for terminal pd across cells with n number of cells in parallel?

Answer 5

V = e = I x r / n

Question 6

What happens each time an electron passes through cells in a circuit with n identical cells in parallel?

Answer 6

• Each time an electron passes through the cells, it travels through one of the cells only ( as the cells are in parallel ).
• Therefore cells act as a source of emf, e and internal resistance r/n.

Question 7

What assumptions are made about silicon diodes?

Answer 7

• Forward pd of 0.6 volts when current passes through it.

* Infinite resistance in reverse direction, or at a p.d less than 0.6 volts in the forward direction.

Question 8

What occurs in a circuit with diodes?

Answer 8

• A pd of 0.6 volts exists across a diode that is forward biased and passing a current.
• Diode that is reverse biased has infinite resistance.