Question 1

Voltage drop testing is being discussed. Technician A connects the red voltmeter lead to the most positive side of the circuit being tested and the black lead to the most negative side or part of the circuit being tested. Technician B says the test must be conducted with the circuit operating with normal amounts of current. Who is correct?

Accepted Answer

Both technicians are correct. Technician A is following the correct procedure for voltage drop testing by measuring the voltage difference between the positive and negative sides of the circuit. Technician B is correct in stating that the test should be conducted with the circuit operating under normal conditions to ensure accurate readings.

Question 2

Resistance checks are being discussed. Technician A says the component must be disconnected from the system before checking. Technician B says an infinite reading means the component is shorted. Who is correct?

Accepted Answer

Technician A is correct. The component should be disconnected from the system before checking for resistance to avoid getting incorrect readings due to readings from other connected components. Technician B is not correct. An infinite reading does not necessarily mean a component is shorted; it could also mean an open circuit or that the component is not connected to the circuit.

Question 3

When using an inductive current probe adapter on a DMM, _____.

Accepted Answer

The thumb wheel on the probe is adjusted to zero on the DMM to ensure accurate current measurement.

Question 4

Oscilloscopes are being discussed. Technician A says the vertical positions represent time. Technician B says the horizontal positions represent voltage. Who is correct?

Accepted Answer

In an oscilloscope, the horizontal axis represents time, and the vertical axis represents voltage, which means both technicians have their descriptions reversed.

Question 5

DMMs that can measure temperature use a _____ adapter that is placed on or near the object to be checked.

Accepted Answer

DMMs that can measure temperature use a thermocouple adapter. This adapter converts the temperature being measured into a voltage that can be read by the DMM. Thermocouples are commonly used in temperature measurement because they are relatively inexpensive, have a wide temperature range, and provide fast and accurate measurements. Other options listed (thermometer, manometer, and refractometer) are not typically used for temperature measurements with a DMM.

Question 6

All the following are lab scope adjustments EXCEPT:

Accepted Answer

Amperage level is not an adjustable setting on a lab scope. The other three, trigger level, slope, and trigger source, are common adjustments on a lab scope.

Question 7

Sensor problems are being discussed. Technician A says a poor ground in the reference voltage circuit can cause higher than normal readings at the computer. Technician B says small amounts of unwanted resistance in a low voltage sensor circuit will not have a significant effect on the vehicle's performance. Who is correct?

Accepted Answer

A poor ground in the reference voltage circuit can cause higher than normal readings at the computer.

Question 8

The wave form of constant DC voltage on a lab scope is a _____.

Accepted Answer

A constant DC voltage is represented on a lab scope as a flat line.

Question 9

A technician is testing a connector in a circuit with a voltmeter. With the power on in the circuit, the meter reads 12 volts when the leads are placed on each side of the connector. This indicates that the connector _____.

Accepted Answer

When a voltmeter reads a voltage across a connector in a powered circuit, it indicates that there is a potential difference, meaning the electrical path is interrupted or open. If the connector were good, there would be no voltage difference across it because it would conduct electricity without resistance.

Question 10

The radiator fan on a vehicle is working, but it is turning at a much slower speed than normal. The specifications for the fan motor are 25 amperes. Your DMM has a maximum amperage of 10 amps. What should you use to test the fan motor current?

Accepted Answer

An inductive type ammeter can measure higher currents without needing to modify the DMM, which is limited to 10 amps.

Question 11

Technician A uses a voltmeter to check circuit resistance. Technician B uses an ohmmeter to check circuit resistance. Who is correct?

Accepted Answer

The answer of Technician A uses a voltmeter to check...

Question 12

What is the best tool to use to find the cause of an intermittent problem in a low-voltage DC circuit?

Accepted Answer

A digital storage oscilloscope is the best tool to use for finding the cause of an intermittent problem in a low-voltage DC circuit because it can capture and display the waveform of the circuit in real-time, allowing for analysis of the voltage and timing of the intermittent issue. A GMM can also be helpful for analyzing the circuit, but it may not capture the waveform with as much detail as a digital storage oscilloscope. A digital voltmeter and test light are useful for measuring voltage and determining if certain components are receiving power, but they may not be able to pinpoint the exact source of the intermittent problem.

Question 13

When testing resistance in a circuit with an ohmmeter, _____.

Accepted Answer

The circuit or component must be disconnected from the power source to prevent damage to the ohmmeter and ensure accurate resistance measurement. The ohmmeter is then connected in parallel with the component being tested.

Question 14

When connecting a conventional ammeter to a circuit, _____.

Accepted Answer

An ammeter must be connected in series to measure current, the circuit should be on for measurement, and the current should not exceed the ammeter's rating to avoid damage.

Question 15

Technician A uses a splice clip while soldering two wires together. Technician B twists the wire strands of the wire ends together before soldering. Who is correct?

Accepted Answer

Both techniques are acceptable methods for preparing wires for soldering. Technician A's use of a splice clip can provide stability and alignment for the wires, while Technician B's method of twisting the wire strands together is a common practice for ensuring a good mechanical connection before soldering.

Question 16

Technician A says jump-starting can cause a battery to explode. Technician B says jump-starting can damage a computer. Who is correct?

Accepted Answer

Jump-starting can cause a battery to explode if done improperly, and it can also damage a vehicle's computer system due to voltage spikes.

Question 17

When testing the high-voltage circuits on a hybrid vehicle, a _____type meter and test leads must be used.

Accepted Answer

When testing the high-voltage circuits on a hybrid vehicle, a Cat III type meter and test leads must be used. Cat III meters are designed to handle transient overvoltages that occur in distribution systems and equipment. They can handle voltage spikes up to 6,000 volts and are suitable for use in industrial environments. It is important to have an appropriate level of protection when working with high voltage circuits to ensure safety. Using a meter with too low of a category rating could result in serious injury or death.

Question 18

When setting up a lab scope to measure a waveform that ranges from 0 to 15 volts; if there are eight vertical divisions, what must the voltage level be set at to display the entire waveform?

Accepted Answer

To display the entire waveform with eight vertical divisions, each division needs to represent 2 volts (15 volts divided by 8 divisions). Therefore, the voltage level needs to be set at 2 volts to display the entire waveform.

Question 19

A technician is checking a circuit with excessive resistance. The current flow through the circuit should be 10 amps, but a check with an ammeter measures only 6 amps. The technician measures a voltage drop of 1.0 volts across the switch terminals when the circuit is turned on. What is the resistance of the switch?

Accepted Answer

According to Ohm's Law, resistance (R) is equal to voltage (V) divided by current (I): R = V/I. In this case, the voltage drop is 1.0 volts and the current flow should be 10 amps, so the resistance should be:

R = 1.0 volts / 10 amps
R = 0.1 ohms

However, the actual current flow is only 6 amps, so we can use Ohm's Law again to solve for the resistance of the switch:

R = V/I
R = 1.0 volts / 6 amps
R = 0.1667 ohms

Therefore, the resistance of the switch is 1/6 ohm, which is answer choice B.

Question 20

The waveform of AC voltage is typically a _____.

Accepted Answer

The most commonly used waveform for AC voltage is a sine wave. This is because most AC sources (such as generators) produce a sine wave, and sine waves have several desirable properties for power transmission and use in electronic circuits. Square waves and sawtooth waves are less commonly used for AC voltage, and a flat line would indicate DC voltage, not AC.

Quiz 16: General Electrical System Diagnostics and Service