PASCO EM-8622 BASIC ELECTRICITY - Manual (Page 37)

33
012-04367E Basic Electricity
Teacher's Guide
Exp 1 - Circuits Experiment Board
➀
➁
Reversing things at either end had no effect.
➃➄
There are two different ways of putting two
lamps into the circuit: parallel and serial.
Parallel:
With this method, the lights will each be approximately
the same brightness as in part 1.
Serial:
Using this circuit, the lights will be dimmer than in part 1.
➤NOTE: It is best to do these experiments with both
batteries, rather than just one. Connect them in series, as
shown in figure 2.1a. This will make the lights brighter
and easier to see when some of the dimmer circuits are
built.
Procedure
➀
➁➂
There are two ways of making the circuit so that both
lights are on with the same intensity.
Series
The lights will be dimmer than in part 1. The electric current
must go through one bulb to reach the other, so disconnecting a
bulb will cause both to go out. (This is how those maddening
“if-one-goes-out-they-all-die-so-Merry-Christmas” lights are
wired.)
Parallel
The lights will show the same intensity as in part 1. The electric
current is going through both bulbs at the same time, so
disconnecting one does not affect the other. (This is how the
Christmas lights you wish you had bought are wired.)
➃➄
Again, the circuit may be series or parallel.
Series Parallel
These circuits have the same characteristics as the ones in part
2-3
➅
There are two ways of doing this as well.
Parallel-in-Series Series-in-Parallel
a b
c
a b
c
(The parallel portion of the first circuit will be very dim.)
What happens if you unscrew one of the bulbs depends on
which bulb you unscrew. In the first circuit, unscrewing (a) will
turn everything off. Unscrewing (b) or (c) will make (a) dimmer
and leave the other one unaffected. In the second circuit,
unscrewing (c) will make (a) and (b) brighter; while unscrewing
(a) or (b) will make (c) brighter and turn the other one off.
➆-➉
Putting the batteries in series (2.1a) will make things
the brightest, because then the voltage to the lights is the
highest. Batteries in parallel (2.1b) will have the same effect
as one battery. Batteries opposed (2.1c) will have no effect
at all unless one of the batteries is nearly dead.
11 The potentiometer, when used this way, adjusts the bright-
ness of the lamp. (For best results, use the batteries in series
for this part of the lab.)
Exp 2 - Lights in Circuits