Lesson 2: General Use Test Instruments

True or False: The higher the resistance in a circuit, the higher the current flow through the circuit.

False The higher the resistance in a circuit, the lower the current flow through the circuit.

One problem with small 3-phase voltage imbalances is that they cause high ? imbalances. a. core b. current c. power d. resistance

b. current Current unbalance is the unbalance that occurs when current on each of the three power lines of a 3-phase power supply are not equal. High current imbalances cause excessive heat, resulting in insulation breakdown.

AC voltage is voltage in a circuit that reverses its direction of flow at regular intervals, and is stated and measured as peak, average, or ? value. a. MIN/MAX b. regular c. rms d. standard

c. rms The rms/root-mean-square/effective value of an AC sine wave is the value that produces the same amount of heat in a pure resistive circuit as DC of the same value.

True or False: Measuring current is useful because only current can be used to determine how much a circuit is loaded (working).

True

True or False: When using an ohmmeter, the resistance of all components connected in parallel with the component being tested affects, and typically lowers, the resistance reading.

True

True or False: When voltage measurements are different from what is expected, the voltage measurement is most likely to be lower than normal.

True

True or False: A portable test instrument is used to take real-time (momentary) measurements.

True A portable test instrument (meter) is a device that is used to take temporary measurements and is typically powered by batteries.

Current is measured in ? . a. amperes b. ohms c. volts d. watts

a. amperes

The ? value of a sine wave is the maximum instantaneous value of either the positive or negative values in the sine wave. a. average b. peak c. positive d. rms

b. peak

True or False: A clamp-on ammeter is typically used to measure current in a circuit with over one ampere of current.

True Clamp-on ammeters and multimeters with current probes are commonly used to measure currents from 1 A or less to 3000 A

True or False: A megohmmeter is a high-resistance ohmmeter used to measure insulation deterioration on various wires by measuring high-resistance values during high voltage test conditions.

True Megohmmeter test voltages range from 50V to 5000V.

True or False: A permanent test instrument is a device that is installed in a process, or at a bench, to continually measure and display quantities.

True Permanent test instruments are powered by a 115 V receptacle.

True or False: A voltage indicator needs only to be near a voltage source to indicate the presence of voltage.

True The advantages of voltage indicators are that voltage indicators are inexpensive, are small enough to carry in a pocket, are easy to use, are nonconductive, and indicate a voltage without touching any live parts of the circuit, even through conductor insulation.

? leakage current is current that flows from areas on conductors where insulation has been removed to allow electrical connections. a. Capacitive b. Conductive c. Surface d. Terminal

c. Surface Conductive leakage current = the small amount of current that normally flows through the insulation of the conductor Capacitive leakage current = leakage current the flows through conductor insulation due to a capacitive effect

Many test instruments include a ? in the current-measuring circuit to prevent damage caused by excessive current. a. bypass b. circuit breaker c. fuse d. relay

c. fuse

A(n) ? is a test meter that measures resistance, the opposition to the flow of electrons in a circuit. a. ammeter b. chronometer c. ohmmeter d. voltmeter

c. ohmmeter

In-line ammeters require the circuit to be ? so the ammeter can be inserted into the circuit to acquire a reading. a. closed b. low voltage c. opened d. parallel

c. opened

An ohmmeter is used to measure the ? . a. amperage b. direction of voltage flow c. resistance d. voltage

c. resistance

True or False: A closed switch that is operating properly has continuity.

True

True or False: Voltage indicators only indicate that voltage and current are present; they do not indicate the actual voltage.

False Voltage indicators only indicate that voltage is present; they do not indicate the actual voltage amount.

True or False: AC current is current in a circuit that flows in one direction only.

False AC (alternating current) is a continually changing current that reverses directions at regular intervals.

True or False: Most analog multimeters do not have calibrated scales that correspond to the different selector switch settings.

False An important part of reading an analog multimeter is verifying that the correct scale is used when reading the measurement.

When a 3-phase current unbalance exceeds ? , a test for voltage unbalance should be performed. a. 3% b. 10% c. 20% d. 30%

b. 10% Likewise, any time there is a voltage unbalance of more than 1%, electricians must test for current unbalance.

Most digital multimeter displays include a(n) ? to show changes and trends in a circuit. a. analog scale b. bar graph c. diode test mode d. MIN MAX mode

b. bar graph

One advantage of voltage testers is that they have a lower impedance (resistance) and draw more current than voltage indicators, which allows them to be used for testing ? . a. insulation b. job order motors c. job order wiring d. GFCIs

d. GFCIs Voltage indicators and multimeters cannot be used to trip GFCIs during a test (when connected from the hot receptacle slot to ground).

Voltage measurements using the ? on a digital multimeter are useful in identifying low voltage conditions. a. analog scale b. bar graph c. diode test mode d. MIN/MAX mode

d. MIN/MAX mode Low voltage conditions can be caused by large motors starting up, by temporary voltage losses, or by circuit overloading or high-voltage surges.

A clamp-on ammeter is a test instrument that measures current in a circuit by measuring the strength of the ? around a single conductor. a. ampacity b. electromotive force c. inductive reactance d. magnetic field

d. magnetic field