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Series Circuits

One after another

ONACD –Editable Curriculum designed for teachers by teachers

http://www.allaboutcircuits.com/vol_1/chpt_5/2.html

ONACD - Editable curriculum designed for teachers by teachers

SeriesFor electrical circuits the term “series” indicates that

components are connected in a way such that current flows in and then out of each component before going on to the next component. If household plumbing was like this you would have to be very carful what order you installed your faucets!

    If voltage is supplied at a constant value, as it typically is,

the following observations for current and total resistance can be made:

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CurrentThe value of current at any point in the circuit will be constant for a series circuit.

There is only one path for the current as it goes through the circuit. Consequently, if there is a break in the circuit the flow of charges stops for the entire circuit.

This plagued older Christmas lights when a bulb would burn out. A newer design causes burned out bulbs to fuse a wire and thus the charges keep flowing and the rest of the bulbs stay lit.

 In a series circuit current is calculated using total voltage

and total resistance with the formula V=IR.

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Total ResistanceThe addition of more resistors into a series circuit increases the total resistance.Each resistor causes a unique drop in the voltage based on its resistance. Resistance converts electrical energy into heat. So each added resistor reduces the amount of current that can flow. Too much resistance on one path will stop the current all together.

 In a series circuit total resistance is calculated by adding the resistors together with a formula like:RT=R1+R2+R3+…

Where RT is resistance total and R1,R2,R3,… are the resistance of each resistor.

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Sample CalculationsConsider the following series circuit with two identical

resistors.  1.What is the total:

a. voltage? 12Vb. resistance? RT = R1+R2

RT = 2+2

RT = 4c. current?

V = IR12 = I(4)12/4 = I3A = I

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1. What is the currenta) at A?

3Ab) at B?

3Ac)at C?

3A

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3.What is the Voltage across:a. A to C?

12Vb. A to B?

V = IRV = (3)(2)V = 6V

c. B to C?

Same resistance so 6V