# how does the current in any one place in the circuit compare to the current at other places in the circuityou have a circuit of battery, switch, light bulb and wires

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An electrical circuit can be series, parallel (the basic configurations) or a combination of series/parallel devices. When finding the current through a circuit one first need to derive its equivalent resistance. For a series circuit the equivalent resistance is

`R_(eq) = R_1+R_2+...+R_n`

while for a parallel circuit the equivalent resistance is

`1/R_(eq) =1/R_1 +1/R_2 +....+1/R_n`

For a complex series-parallel circuit the equivalent resistance is found by grouping together the resistances first in series and parallel combinations then finding the total resistance of these groups.

The total current in circuit is given by the Ohm law:

`I_("tot") =U_("tot")/R_(eq)`

For a series circuit the current is the same in all the components while the different voltage drops on the components add together to give the total supply voltage.

For a parallel circuit the voltage is the same in all components (and equal to the supply voltage) while the different currents through components add together to give the total current.

For a complex series-parallel circuit the voltages and currents split accordingly the above rules on to different existent series and parallel resistor groups.

this sounds like a basic series circuit, so, as long as the switch is closed the current should be constant at any and every point around the circuit. Current is simple the number of charges (electrons) that pass a point in the circuit every second. A high current means lots of electrons per second, low current- less electrons per second.

High resistance components slow down the flow of electrons through them but the magical thing about electricity is that this effect is averaged out over the whole circuit so the current before going through the component has already been reduced as though it has already been through the resistor. Almost as if the effect happened before the cause!