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Voltage, Current, Resistance
Slide 1
Diagram showing relationship between the voltage current and resistance in a circuit.
In 1827, Georg Ohm successfully showed that there was a simple relationship between the voltage current and resistance in a circuit.
This became known as…
Ohm's Law
The Current (I) in an object at constant temperature is proportional to the potential difference (V) across its end.
Resistance is then defined as R = V / I
Slide 2
Diagram showing relationship between the voltage current and resistance in a circuit.
The circuit shown is the simplest possible electrical circuit.
Battery: a battery which supplies the electrical force to the circuit, measured in volts.
Current: the direction of the circuit current, always shown form +ve to -ve.
Resistance: a resistance which opposes the force of the battery and hence the flow of the current.s
Slide 3
The following are the elements of Ohm's Law showing typical values for a 19th century transatlantic cable…
V = Voltage: the voltage supply came from a number of batteries in series and was normally around 30 volts
I = Current: typical current level over 2000 miles was between 4 and 8mA (milliamps)
R = Resistance: typical line resistance was 2 ohms per mile, so on a transatlantic cable of 2000 miles, overall resistance was around 4000 ohms
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