When a circuit has a reactive component (Inductive or Capacitive) its current rises and falls out of sync or phase with the voltage that causes that current to flow. The further out of phase this current is with the voltage the less effective it becomes and where possible we try to correct the effects of a reactive component by adding a component with an equal and opposite reactive component and bring the current and voltage sine waves closer together.
This interactive tool starts by showing two sine waves (brown for Voltage and Black for current) which are in phase with each other. By moving the black slider on the left you can see the values of both and the Power (V x A) over one cycle. As both pass through maximums and zeros at the same point in time this means that overall the sum of the powers in the cycle will be optimal.
By clicking on the Offset Current check box on the left hand side a new (Green) current sine wave is drawn on the diagram. By sliding the green offset slider on the right hand side this new current sine wave can be offset (from 90 degrees lagging to 90s degrees leading).
Having set the offset slider away from its default "in phase" value move the black sine wave slider on the left and see how the Green Offset Current changes in relation to the original Black (in phase) current sine wave and how the two Power values compare over one full cycle.
Whilst there will be some parts of the sine wave where the Green Power value is greater than the Black Power value most of the time it will be the other way around. This should be more obvious when you realise that when offset the Power will be zero at 4 points each cycle instead of the 2 in the "in phase" version as it becomes zero whenever voltage or current waves are at zero. With the "in phase" version these point coincide so only occur twice wheras in the offset version the voltage or current zeroes never coincide so you will have four zero power points in the cycle. Whilst its almost impossible to achieve 90 degrees displacement if acheved the currents are zero when voltage is at a maximum and vice versa therby cancelling out the four potential points of maximum power.
