360 Section 3 Fundamentals of Electricity and Electronics
❚ A voltmeter must be connected in parallel with
the circuit. A conventional ammeter must be con-
nected in series with the circuit. An inductive
ammeter has a lead that clips over the outside of
the wire. An ohmmeter must not be connected
to a source of power. It uses internal batteries to
measure circuit or component resistance.
❚ Voltage drop measurements provide an easy way
of checking for high resistance. You do not have
to disconnect the power source and isolate the
component, as with an ohmmeter. A high voltage
drop indicates a high resistance. A low voltage
drop indicates a low resistance.
❚ Learning how to perform basic tests on connec-
tors, resistors, switches, fuses, and other basic
components will help you understand how to test
more complex components.
Technical Terms
Write the defi nitions for the following terms on a
separate sheet of paper.
Activities
1. While wearing rubber gloves and eye
protection, measure the voltage of two
old car batteries. Write down the voltage
reading for each. Charge both batteries for
15 minutes, then recheck the voltage. Do
both batteries charge up at the same rate?
Recharge both batteries for two hours and
repeat your voltage measurements. Write a
short paragraph on your fi ndings.
2. While wearing safety gear, measure the
resistance of a temperature sensor at
room temperature. Record you resistance
reading. Using a heat gun, heat the sensor
to 100°F, and record the sensor resistance
reading. Does the sensor seem to be
working? Write a paragraph on your
fi ndings.
Review Questions
Answer the following questions using the
information provided in this chapter .
1. What are fi ve questions you might ask
yourself when trying to fi nd a problem?
2. If only one component does not work,
where should you start your tests?
3. If more than one component does not work,
where should you start your tests?
4. What effect does an open circuit have on
current?
5. What six conditions may cause an open
circuit?
6. What might make a bulb glow dimly or a
motor run slowly?
7. Explain how a short might cause an
electrical fi re.
8. What is an intermittent problem?
9. How would you use a jumper wire to check
a switch?
10. Which testing device usually provides the
quickest and easiest way to check a circuit
for continuity?
11. Which testing device uses a signal
generator and inductive pickup to fi nd
shorts and opens in wires?
12. Explain how to connect a conventional
ammeter and an inductive ammeter to test
a circuit.
13. An ohmmeter shows a reading of 2.500 kΩ.
What is the meter reading in ohms?
14. Explain how you can use voltage drop
measurements to determine whether a
switch is functioning correctly.
15. List eight rules for using multimeters.
16. Which type of multimeter should be used
to check for voltage in a computer circuit?
17. Explain how to use a test light to check a
connector.
ammeter
auto ranging
contact cleaner
electrical diagnosis
electrical solvent
freeze spray
grounded circuit
hot wire short to ground
infi nite resistance
intermittent problem
jumper wire
ohmmeter
open circuit
short circuit
test light
transducer switch
voltage drop
measurement
voltmeter
zero resistance