Ohm's Law

[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]