A student does an experiment to determine the resistance of a fixed resistor, R. The student draws an incomplete diagram of the circuit, as shown in the figure below.
On the figure, draw the missing circuit symbols.
Describe how the student could use the circuit to determine a reliable value for the resistance of R.
The figure below shows a 
resistor connected to a power supply.
A second resistor is connected in series with the first. State and explain how this affects the current in the circuit.
and the potential difference 
. He can then calculate the resistance 
of the resistor by:
and 
are the average values of the voltage and the current.
.
