Answers to GCSE Series Circuits

Practice Questions

1.State the value for the current for ammeter A₁ in the circuit below:

The current should flow from positive terminal of cell around to the negative, in this case the anticlockwise direction. However, the diode has been placed so that the current would have to pass through in the high resistance direction. This will mean that a current cannot flow, so the reading on A₁ will be 0A. 

2. Calculate the potential difference across the cell for voltmeter V₁, using the cell diagram below.

In a series circuit the potential difference across the cell is shared between the components. So, total potential difference across the cell = 5V + 7V = 12V.

3. The total resistance of a series circuit is 35 ohms. There are 3 resistors in series, that each have their own resistance value in the ratio of 4:2:1. Calculate the resistance of each resistor.

Total resistance in a series circuit is the sum of the individual resistors. 

If ratio is 4:2:1, then there are 4+2+1 = 7 parts in total

35/7 = 5 ohms per part

Resistor (4 part ratio) = 5 x 4 = 20 ohms

Resistor (2 part ratio) = 5 x 2 = 10 ohms

Resistor (1 part ratio) = 5 x 1 = 5 ohms

So resistance is shared 20 ohms:10 ohms:5 ohms