PASCO EM-8622 BASIC ELECTRICITY - Manual (Page 33)

29
012-04367E Basic Electricity
The labs asking for relative brightness ask students to
judge relative brightness only, not an absolute brightness.
This part of the experiment would be aided by having the
room mostly darkened. Additional bulbs can be pur-
chased from PASCO, at Radio Shack, an electronics
store, at auto supplies stores, or possibly a local discount
store.
Batteries
The Circuits Experiment Board is designed to use one or
two D-cells. The voltage delivered by a D-cell is 1.5
volts ±. In practice, alkaline cells give the longest life,
but the less expensive zinc-carbon cells will give ad-
equate results. A single set of batteries was used success-
fully by ten different classes to complete labs 1,3,4,5, 6
and 7 before being replaced.
Resistors
The resistors supplied are listed under Materials on page
1 of this manual. The values have been chosen for clear
results and for helping to extend the life of the D-cells. If
resistors are lost or broken, replacements can be pur-
chased from PASCO, or at any electronics store, includ-
ing Radio Shack. Other values can be substituted, but for
Experiments 3 through 7, the values should be between
100
Ω
and 1500
Ω
for best results.
➤NOTE: Using the 330 Ω
, 560
Ω
and 1000
Ω
resistors gives approximate ratios of 1:2:3 for
working towards semi-quantitative understanding
of d.c. circuits.
The diagram below shows the resistor color code. For
example, a resistor having the colors Orange-Orange-
Brown-Silver has the value 330
Ω
± 10%.
Appendix: Tips and Troubleshooting
Correct Circuit, Doesn’t Work
• Check to see if the circuit is indeed connected cor-
rectly and completely.
• Check to see if the battery is giving full voltage.
• Check to see if each wire is making contact with the
spring. If magnet wire is used, the enamel coating
on the outside will prevent electrical connection and
needs to be removed. In some cases, students may
try to make a complete circuit through the insulation.
Surprising Results
In some cases, there will be no difference in the measure-
ments from one point in the circuit to another. This
doesn’t mean the measurement is trivial or unimportant,
rather it is what we hope the student will learn from his/
her lab work. Not all measurements have to be different.
Making a “switch”
In the several labs, students are asked to use a “vacant”
spring connection such as one of the three around the
transistor socket as shown on the right as a “switch.” By
connecting one lead from the battery there and then
taking a third wire to the circuit, you can effectively
switch the power “on” and “off” by simply connecting or
not connecting the third wire. This duplicates the action
in a real switch.
Lights and Relative Brightness
The lights for this experiment board, #14 bulbs, are
designed for 2.5 volts and 0.3 amperes. A single D-cell
will not light a bulb to maximum brightness, but two cells
in series will give a very bright light.
➤ ➤
“Switch”
Figure 2
Can be
removed
1st Digit
2nd Digit
No. of Zeros
Tolerance
0
1
2
3
4
5
6
7
8
9 Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Gray
White
None
Silver
Gold
Red
±
20%
±
10%
±
5%
±
2%
Fourth Band
Figure 3