[table]
[tr]
[td][h3]V[/h3][/td][td]Voltage, Potential Difference, P.D, V[/td]
[/tr]
[tr]
[td][h3]I[/h3][/td][td]Current, Amps, A[/td]
[/tr]
[tr]
[td][h3]R[/h3][/td][td]Resistance, Ohms, [ohm][/td]
[/tr]
[/table]
The relation of the three is shown through the following formulae:
[code]
V = I [multiply] R
[/code]
or
[code] I = V [divide] R[/code]
or
[code]
R = V [divide] I
[/code]
[u]Resistance:[/u]
[ul]
[li]Resistance is measured in Ohm's ([ohm])[/li]
[li]Resistance opposes current flow[/li]
[li]Named after George Ohm c.1830[/li]
[li]Discovered the relationship between Potential Difference and Current[/li]
[li]The higher the resistance the lower the current flow[/li]
[li]The lower the resistance the higher the current flow[/li]
[li]Resistance occurs when electrons from the current collide with ions in the substance it is traversing through[/li]
[li]If the temperature is higher, the ions vibrate more, and the electrons collide more often, causing higher resistance[/li]
[/ul]
[b]Ohm's Law States:[/b]
[highlight]
"The [b]potential difference[/b] across a device is directly proportional to the current flowing through it, provided the resistance remains constant"
[/highlight]
[u]Unit conversion:[/u]
5.6M[ohm] = 5.6[multiply]10^6[ohm]
100mA = 100[multiply]10^-3A ---> 0.1A
5.3kV = 5.3[multiply]10[cubed]V ---> 5300V
[h3]Examples[/h3]
[highlight]
[b]Example 1:[/b]
The current of a circuit is 2 [b]amps[/b] and the [b]voltage[/b] is 12, work out the [b]resistance[/b].
[table]
[tr]
[td][b]R[/b][/td][td]=[/td][td style='text-align:left'] [b]V[/b] [divide] [b]I[/b][/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']12 [divide] 2[/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']6[ohm][/td]
[/tr]
[/table]
[/highlight]
[highlight]
[b]Example 2:[/b]
The resistance of a circuit is 12[ohm] and the current is 0.1 [b]amperes[/b], work out the [b]potential difference[/b].
[table]
[tr]
[td][b]V[/b][/td][td]=[/td][td style='text-align:left'] [b]I[/b] [divide] [b]R[/b][/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']0.1 [multiply] 12[/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']1.2V[/td]
[/tr]
[/table]
[/highlight]
[highlight]
[b]Example 3:[/b]
The [b]potential difference[/b] of a circuit is 12 and the resistance is 4[ohm]'s, work out the current.
[table]
[tr]
[td][b]I[/b][/td][td]=[/td][td style='text-align:left'] [b]V[/b] [divide] [b]R[/b][/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']12 [divide] 4[/td]
[/tr]
[tr]
[td][/td][td]=[/td][td style='text-align:left']3 amps[/td]
[/tr]
[/table]
[/highlight]