Explanation

By moving the slider for the voltage investigate how the current flowing through each lamp increases and how this increase in current increases the brightness of the lamps. This is an example of Ohms Law

Now alter the resistance slider of one of the lamps and see how decreasing the resistance increases the current (again as per Ohms Law). The current flowing through both lamps is dependant upon the equivalent resistance of the two lamps in series and the voltage applied across them by the battery.

Note how the voltage drops across the lamps changes with a change in resistance but their sum always equals that of the voltage supplied by the battery.

Note how when the resistance values of the lamps differ from each other they have different brightnesses. The brightness is related to the power consumed by each lamp which is calculated by multiplying the current flowing the lamp multiplied by voltage dropped across each lamp. The same current flows through each lamp wired in series so the power and brightness is based on the voltage across each lamp.

These voltage can be worked out using Ohms Law and multiplying the resistance of each lamp by that current flowing through both lamps.

Set the Battery Voltage to 24V and both lamp resistances to 6 Ohms. 2A flows through the circuit and the voltage dropped across each lamp is 12V (2A multiplied by 6 Ohms).

Now reduce the resistance of just one of the lamps to 2 Ohms, the equivalent resistance is now 8 Ohms meaning 3A will flow through both lamps.

You will notice one lamp is far brighter than the other. This is because the voltage dropped across both lamps is now no longer evenly split between them but in proportion to the resistances. The 2 Ohm resistance lamp has a wattage of 18W (3A mutiplied by 6V) whilst the other has a wattage of 54W (3A mutiplied by 18V)

If you were to reduce the resistance down to nothing the equivalent resistance would be just the 6 Ohms of the remaining lamp meaning all 24V would be dropped across that lamp meaning it would glow brighter still as it would use 96W (4A mutiplied by 24V).

Electrical Lighting circuits DO NOT have lamps wired in series as one lamp blowing would prevent the other woring. Plus they have a rated voltage that they should be fed at which is tricky if they are wired in series.

Note how Ammeters and Voltmeters are connected into the circuit differently.