Investigating Components

Question 1

True or false? An ammeter must be connected in parallel with a component to measure the current in that component.

Answer 1

False

An ammeter must always be connected in series with a component.

Question 2

On an I-V graph, do you plot current on the x-axis or the y-axis?

Answer 2

The y-axis
The current is the dependent variable that you measure when you change the potential difference, and so it has to be plotted on the y-axis

Question 3

Briefly describe an investigation you could do to plot an I-V graph for a component.

Answer 3

Set up a test circuit made up of a variable power supply, the component and an ammeter all connected in series. Connect a voltmeter in parallel with the component to measure the potential difference across it. Take pairs of readings from the ammeter and voltmeter as you alter the potential difference of the power supply.

Question 4

Which variable would you need to control if you did this investigation for an LDR?

Answer 4

The light level in the room

Question 5

Describe how, after plotting an I-V graph for a thermistor, you could use your circuit to investigate how the resistance of the thermometer varies with temperature.

Answer 5

Set the supply potential difference to a constant value, and then gradually heat the thermistor. Measure the current on the ammeter and the temperature of the thermistor as it increases. Calculate the resistance by dividing the potential difference by the current.