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Series Circuit

add it up


Learn about series circuits and voltage dividers

Essential Keywords

  • Voltage
  • Current
  • Series
  • Voltage Divider


We talked about Voltage being like a hill and the Battery puts the ball on top of the hill. We could also compare to items on a shelf. We can have the low shelf and a top shelf and anything in between. If one battery puts the ball on the first shelf, we can add a second battery to put it to the second shelf. A 4 battery pack is like a 4 shelf high system. Adding voltages on top of each other is a Series Circuit .

4 AA battery

The typical Battery Pack puts the batteries in Series. A single AA battery is about 1.5 Volts. When we connect four in Series we get about 6 Volts.

Voltage Divider Circuit

Resistors can also be arranged in Series. In this case the value of the resistors adds up. So if each resistor is 100k then a series stack of five would be 500k. In a series circuit the current is the same in each resistor so from ohms law

V = I * R 

You can see that the voltage is shared or divided among the resistors in the series stack. If they are all equal they will each have an equal voltage.

Divider Schematic

Here is the schematic diagram of the 4 batteries and 5 resistors in series.

we can implement this on a breadboard circuit and show how the voltage divides among the equal resistors

Divider and meter

Here we have our 5 resistor voltage divider circuit implemented on a breadboard. We have used our electronic power supply to provide 5 Volts. A meter is connected to the top of the divider and the ground reading the full voltage that is about 5 Volts.

divider 4 resistor

Here we have moved the meter connection down the series stack by one resistor. All of the resistors are equal so we have just stepped down 1/5 of the voltage leaving about 4 Volts.

3 resistor divider

Similarly the next step gives about 3 Volts. The slight differences you are seeing from the expected voltage is due to the resistors not being perfectly equal.

battery voltage divider

Here is a similar set up using the battery pack.


First complete the measurements on the 5 equal resistor divider the next 2 steps. Then try different values of resistors to make your own divider. Make a divider circuit that gives us 1/10 of the voltage to provide a 10 x range for voltage measurements.