Download Parallel vs. Series Circuits

Parallel vs. Series Circuits
Only a licensed professional electrician like this
one is qualified to install or repair the electrical
system inside a home. It’s a complicated system
that consists of a maze of electric circuits.
One Loop or Two?
An electric circuit consists of at least one closed loop through which electric current can flow.
Every circuit has a voltage source such as a battery and a conductor such as metal wire. A circuit
may have other parts as well, such as lights and switches. In addition, a circuit may consist of
one loop or two loops.
Series Circuit
A circuit that consists of one loop is called a series circuit. You can see a simple series circuit
below. If a series circuit is interrupted at any point in its single loop, no current can flow through
the circuit and no devices in the circuit will work. In the series circuit below, if one light bulb
burns out, the other light bulb won’t work because it won’t receive any current. Series circuits
are commonly used in flashlights. You can see an animation of a series circuit at this URL:
http://regentsprep.org/regents/physics/phys03/bsercir/default.htm
Q: If one light bulb burns out in this series circuit, how can you tell which bulb it is?
A: It may not be obvious, because neither bulb will light if one is burned out. You can tell which
one it is only by replacing first one bulb and then the other to see which replacement results in
both bulbs lighting up.
Parallel Circuit
A circuit that has two loops is called a parallel circuit. A simple parallel circuit is sketched
below. If one loop of a parallel circuit is interrupted, current can still flow through the other loop.
In the parallel circuit below, if one light bulb burns out, the other light bulb will still work
because current can bypass the burned-out bulb. The wiring in a house consists of parallel
circuits. You can see an animation of a parallel circuit at this URL:
http://www.regentsprep.org/regents/physics/phys03/bparcir/default.htm
Summary
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An electric circuit consists of one or two closed loops through which current can flow. It
has a voltage source and a conductor and may have other devices such as lights and
switches.
A circuit that consists of one loop is called a series circuit. If its single loop is interrupted
at any point, no current can flow through the circuit.
A circuit that consists of two loops is called a parallel circuit. If one loop of a parallel
circuit is interrupted, current can still flow through the other loop.
Vocabulary
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parallel circuit: Electric circuit that has two loops through which current can flow.
series circuit: Electric circuit that has only one loop through which current can flow.
Practice
Take the quiz at the following URL and then check your answers.
http://www.twothirtyvolts.org.uk/education/revision-quiz/electric-circuits-11to14.html
Review
1. Compare and contrast series and parallel circuits.
2. Create a sketch of a parallel circuit that contains a voltage source and two light bulbs.