Current plotted against PD for a bulb

Download bulb.ddw

Datadisc can easily record two parameters against each other:

We can calculate the resistance of the bulb as it varies with PD by dividing each PD value by its corresponding current value. Select Data: Calculate and click the button. Make sure that the correct channels are selected for the a and b values and click Calculate.

Graph of data

Close the Calculation window and view the new data. For this bulb, the resistance varies from less than 2 cold to over 7 when running.

(Graph: Set axes has been used to select joined points for the resistance plot.)