Current, Charge and Time

[table] [tr] [td][h3]Q[/h3][/td][td]Charge, Coulombs, C[/td] [/tr] [tr] [td][h3]I[/h3][/td][td]Current, A[/td] [/tr] [tr] [td][h3]T[/h3][/td][td]Time, seconds, s[/td] [/tr] [/table] Electrical charge ([b]C[/b])is the amount of electrons in the circuit (the charge). One [b]Coulomb[/b] contains [b]6.24[multiply]10^18 electrons[/b]. How much and for how long it flows is depends on the other 2 factors, [b]time[/b] and [b]current[/b]. The relationship between the 3 variables is shown by this equation: [code] Q = I [multiply] T [/code] which can be rearranged to: [code] I = Q [divide] T [/code] or: [code] T = Q [divide] I [/code] [h3]Current[/h3] [u]Current is the rate of flow of charge[/u] Effects of current: [ul] [li]Heating[/li] [li]Chemical[/li] [li]Magnetic[/li] [/ul] [hr] Using the formulae, one can find out the values of a desired variable if they possess the other 2. [h3]Examples[/h3] [highlight] [b]Example 1[/b] [code] [b]I[/b] = 5mA [b]Q[/b] = 25mC [/code] First convert these into normal numbers: [b]I[/b] = 5[multiply]10^-3 = [u]0.005 amps[/u] [b]Q[/b] = 25[multiply]10^-3 = [u]0.0025 coulombs[/u] [table] [tr] [td][b]T[/b][/td][td]=[/td][td style='text-align:left'][b]Q[/b] [divide] [b]I[/b][/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']0.025 [divide] 0.005[/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']0.2s[/td] [/tr] [/table] [/highlight] [highlight] [b]Example 2[/b] [code] Calculate the charge flowing when a current of 3 [b]amperes[/b] flows for 4 [b]seconds[/b] [/code] So we have: [ul] [li]3 amps[/li] [li]4 seconds[/li] [/ul] and we need to find how much charge is flowing [b](Q)[/b]. [table] [tr] [td][b]Q[/b][/td][td]=[/td][td style='text-align:left'][b]I[/b] [multiply] [b]T[/b][/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']3 [multiply] 4[/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']12 coulombs[/td] [/tr] [/table] [/highlight] [highlight] [b]Example 3[/b] [code] Calculate the current flowing if a charge of 6 [b]coulombs[/b] flows in 2 seconds [/code] So we have: [ul] [li]6 coulombs[/li] [li]2 seconds[/li] [/ul] and we need to find how much current is flowing [b](Amps)[/b]. [table] [tr] [td][b]I[/b][/td][td]=[/td][td style='text-align:left'][b]Q[/b] [divide] [b]T[/b][/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']6 [divide] 2[/td] [/tr] [tr] [td][/td][td]=[/td][td style='text-align:left']3 amps[/td] [/tr] [/table] [/highlight]