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# Relative vs. Absolute Voltage

## Electric circuits and the voltage at any point

### Absolute Voltage

If voltage at point A is quoted with reference to the earth point - the absolute potential - then the voltage is written UA.

### Relative Voltage

If voltage at point A is quoted with reference to point B - then the voltage is written UAB.

### Example - Relative and Absolute Voltage

The total resistance in the series circuit above can be calculated

R = (33 ohm) + (47 ohm) + (33 ohm)

= 113 ohm

The current in the circuit can be calculated

I = (12 volts) / (113 ohm)

= 0.11 ampere

The relative voltage between point A and BVAB - can be calculated

UAB = (33 ohm) (0.11 ampere)

= 3.6 volts

The absolute voltage in point A relative to earth is

UA = 12 V

The absolute voltage in point B relative to earth is

UB = UA - UAB

= (12 volt) - (3.6 volt)

= 8.4 volt

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