13.4 More circuit calculations

Question 1

Cell current =

Answer 1

Cell emf / total circuit resistance

Question 2

Pd across each resistor in series with the cell =

Answer 2

Current x the resistance of each resistor

Question 3

Pd across the parallel combination =

Answer 3

Current through each resistor x resistor’s resistance

Question 4

If the cells are connected in the same direction in the circuit, the net emf is…

Answer 4

…the sum of the individual emfs.

Question 5

If the cells are connected in opposite directions to each other in the circuit, the net emf is…

Answer 5

…the difference between the emfs in each direction

Question 6

The total internal resistance is the…

Answer 6

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

Question 7

For a circuit with n identical cells in parallel, the current through each cell =

Answer 7

I/n

In which:
I is the total current supplied by the cells
r is the internal resistance of each cell

Question 8

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

Answer 8

Electron
emf
Internal resistance

Question 9

A diode that is reverse-biased has ______ resistance

Answer 9

Infinite

Question 10

What are Kirchhoff’s laws

Answer 10

At any junction in a circuit, the total current entering the junction is equal to the total current leaving the junction

For any complete loop in a circuit, the sum of the emfs around the loop is equal to the sum of the potential drops around the loop