Series and parallel circuits
• Old Christmas lights-when one bulb
burned out, the whole string would not
work (which burned out?)
• This is because they were connected in a
series circuit
– Only 1 pathway for current to follow
– If one bulb burns out, the circuit is broken
Series
Parallel
Series Circuits
• In a series circuit, there is a single
pathway for the electrons to flow from
beginning to end.
• When cells are connected in series, the
voltage of the cells is added together.
• When components are connected in
series, the voltage is divided between
them.
– That is, two identical light bulbs connected in
series will each glow half as brightly as a
single bulb.
A simple series circuit
•Another drawback: as devices are added, the
overall resistance increases, which decreases
current
-Eg: Bulbs dim, motors slow
Parallel circuits
• Each item has its own current pathway
• This has 2 advantages over series circuits:
1. Breaking the pathway for one device
does not affect other devices
2. Adding more items does not increase
circuit resistance
-it decreases resistance by adding
more pathways
Parallel circuits
• Disadvantage: they require more
conducting wire
• In a kitchen wired in series, what would
happen when the lights were turned off?
– Everything else would turn off too!
Parallel Circuits
• In a parallel circuit, there is more than one
pathway on which electrons can flow.
• When cells are connected in parallel, the
voltage remains the same as the highest
single cell, but the cells will last longer.
• When components are connected in parallel,
the voltage delivered to them is not reduced.
•
That is, two identical light bulbs connected
in parallel will each glow as brightly as a
single bulb.
SERIES CIRCUIT
ONLY ONE PATH FOR CURRENT TO FLOW
IF ONE GOES OUT THEY BOTH
GO OUT
PARALLEL CIRCUIT
MORE THAN ONE PATH FOR CURRENT TO FLOW
IF ONE LIGHT GOES OUT THE
OTHER STAYS ON
Series and Parallel Circuits
A ___mA
A
___mA
A
___mA
A ___mA
When more lamps are added in series, the
total current __creases.
There is ____pathway, and the current is
_____ _______ at all locations.
A ___mA
A
__mA
A __mA
A
__mA
A __mA
A
__mA
Now there are __ conducting pathways. When
more lamps are added in parallel, the current
next to the cells __creases.
A
A
__mA
A
A
__mA
A
__mA
As more cells are added in parallel, the
total current ___ creases.
__Lamps in _________________
A
__mA
A
A
A
__mA
__mA
__mA
If one lamp burns out, will the rest stay
lit? ___________________