Pre-test For Avionics Specialists Quiz

The aircraft instrument panel is electrically bonded to the aircraft structure in order to provide current return paths. This is important for the proper functioning of electrical systems in the aircraft. By providing a low resistance path for the flow of electrical current, the instrument panel ensures that the current can easily return to its source, preventing any potential electrical issues or malfunctions.

When electric cables pass through holes in various structures, it is important to protect them from chafing. Wrapping the wires with plastic or electrical tape may provide some level of protection, but the most suitable method is to use a grommet. A grommet is a ring or sleeve made of rubber or other materials that is inserted into the hole. It acts as a cushion and prevents the cables from rubbing against the sharp edges of the hole, reducing the risk of damage or wear on the wires.

When the (+) terminal of a voltmeter is connected to the (-) terminal of the source voltage and the (-) terminal of the meter is connected to the (+) terminal of the source voltage, the voltmeter will read "backwards." This is because the voltmeter measures the potential difference between two points, and by reversing the connections, the polarity of the voltage being measured is also reversed. As a result, the voltmeter will display a negative reading or a reading in the opposite direction of the actual voltage.

The instrument discrepancies that would require replacement of the instrument are case leaking, glass cracked, will not zero out, and fogged. Case leaking indicates a problem with the integrity of the instrument's housing, which could lead to further damage or malfunction. A cracked glass can impair visibility and compromise the accuracy of the instrument. If an instrument will not zero out, it cannot provide accurate readings. Fogging inside the instrument can indicate moisture infiltration, which can damage internal components and affect performance. Therefore, these discrepancies would necessitate replacement of the instrument.

Milliampere is the term that represents .001 ampere. The prefix "milli-" indicates a factor of 1/1000, so a milliampere is equal to 0.001 amperes.

Circuit breakers, fuses, and current limiters are the three most commonly used circuit-protection devices in aircraft circuits. Circuit breakers are designed to interrupt the flow of current when it exceeds a certain threshold, protecting the circuit from damage. Fuses are also designed to interrupt the flow of current, but they do so by melting a metal strip when the current exceeds a certain level. Current limiters, on the other hand, are used to limit the amount of current flowing through a circuit, preventing it from reaching dangerous levels. Together, these three devices help to ensure the safety and reliability of aircraft circuits.

A megohmmeter is used for measuring very high values of resistance. This instrument is specifically designed to measure resistances in the range of megaohms, which is much higher than what a regular multimeter or shunt type ohmmeter can measure. The megohmmeter applies a high voltage to the resistance being measured and measures the resulting current flow. By using this high voltage, it is able to accurately measure extremely high resistances that cannot be measured with other instruments.

To locate the leak(s) in a static pressure system, isolating portions of the line and testing each portion systematically, starting at the instrument connections is the correct approach. By isolating different sections of the line and testing them individually, it becomes easier to identify the specific portion where the leakage is occurring. This method allows for a systematic and targeted approach to locating and addressing the leaks in the system.

Electric wire terminals for most aircraft applications must be ring type because they provide a secure and reliable connection. The ring terminals have a circular shape that allows them to be easily attached to screws or studs, ensuring a tight and stable connection. This is crucial in aircraft applications where vibrations and movements can occur. The ring terminals also provide a larger contact area, reducing the risk of loose connections or electrical faults. Therefore, using ring terminals is essential to maintain the safety and functionality of the electrical systems in aircraft.

The instruments connected to an aircraft's pitot static system are the vertical speed indicator, altimeter, and airspeed indicator. The vertical speed indicator measures the rate of climb or descent of the aircraft. The altimeter measures the altitude of the aircraft above sea level. The airspeed indicator measures the speed of the aircraft through the air. The cabin altimeter and cabin rate-of-change indicator are not connected to the pitot static system.

A rectifier is an electrical device that converts alternating current (AC) into direct current (DC). AC is the type of current that constantly changes direction, while DC flows in only one direction. By changing the AC to DC, a rectifier allows for the utilization of DC power in various electronic devices and systems. This is achieved by using diodes, which are electronic components that only allow current to flow in one direction. Therefore, the correct answer is that a rectifier changes alternating current to direct current.

Diodes are primarily used as rectifiers in electrical power supply circuits. A rectifier is a device that converts alternating current (AC) into direct current (DC). It allows current to flow in only one direction, blocking the reverse flow. This is achieved by the diode's characteristic of having a low resistance in the forward direction and a high resistance in the reverse direction. By rectifying the AC power, the diode ensures that the electrical devices connected to the power supply receive a steady and consistent flow of DC power.

The square root of a number is the value that, when multiplied by itself, gives the original number. In this question, we are asked to find the square root of 16 raised to the fourth power. 16 raised to the fourth power means multiplying 16 by itself four times. The square root of that value would be the number that, when multiplied by itself, gives the result of 16 raised to the fourth power. Therefore, the correct answer is 256, as 256 multiplied by itself four times equals 16 raised to the fourth power.

Crimping is the most common method of attaching a pin or socket to an individual wire in an MS electrical connector. This involves using a crimping tool to squeeze the metal sleeve of the connector onto the wire, creating a secure and reliable connection. Crimping is preferred over soldering because it is quicker, easier, and less prone to heat damage. Additionally, crimped connections can be easily inspected and repaired if necessary. Soldering may be used in certain situations, but it is not as commonly used as crimping in MS electrical connectors.

The formula VD = RLA is used to calculate the voltage drop. In this case, the resistance per foot (R) is given as .00644. The length of the wire (L) is 50 feet and the amperes (A) is 12.5. Plugging in these values into the formula, we get VD = .00644 * 50 * 12.5 = 4V. Therefore, the voltage drop for a No. 18 copper wire 50 feet long to carry 12.5 amperes is 4V.

Guarded switches are the correct answer because they provide an extra layer of protection against inadvertent activation or accidental operation of the circuit. These switches are designed with a protective cover or guard that prevents them from being easily toggled or pressed, reducing the risk of unwanted activation. This feature is particularly important in emergency circuits where the consequences of accidental activation could be severe. Spring-loaded switches and push-pull type circuit breakers may not offer the same level of protection as guarded switches, making them less suitable for circuits that require strict control to prevent unintended operation.

Capacitors are used in DC circuits to smooth out slight pulsations in current/voltage. When there are small variations in the current or voltage, capacitors can store and release electrical energy to even out these fluctuations, resulting in a more stable and constant output. This helps to prevent rapid changes in the circuit and ensures a more consistent flow of current or voltage.

Impedance is the correct answer because it refers to the combined resistive forces in an AC circuit. It includes both resistance and reactance, which are the two components that oppose the flow of current in an AC circuit. Resistance is the opposition to the flow of current caused by the circuit's components, while reactance is the opposition caused by the circuit's inductance and capacitance. Impedance takes into account both of these factors and represents the total opposition to current flow in an AC circuit.

AN/MS electrical connectors are specifically designed to meet military specifications. These connectors are built to withstand harsh environments and provide reliable electrical connections in military applications. Military specifications ensure that the connectors meet the required standards for durability, performance, and compatibility with other military equipment. These connectors are commonly used in military aircraft, vehicles, and other defense systems where reliable electrical connections are crucial for mission success.

The advantage of a current limiter is that it can handle an overload for a short period of time. This means that if there is a sudden surge in current in a circuit, the current limiter will be able to handle it and prevent damage to the circuit. However, it is important to note that this capability is only for a short period of time, and the current limiter may not be able to sustain the overload for an extended period.

The correct answer is "Current rating with the contacts closed". The nominal rating of electrical switches refers to the maximum amount of current that the switch can handle when the contacts are closed. This rating indicates the switch's ability to safely carry the specified current without overheating or causing any damage. It is important to consider this rating when selecting a switch for a specific application to ensure it can handle the required current load.

The starter circuit does not contain a fuse or circuit breaker. The starter circuit is responsible for initiating the engine's rotation and does not involve any electrical components that would require protection from overcurrent.

The output of an INS (Inertial Navigation System) can be fed to attitude indicators. Attitude indicators display the orientation of an aircraft with respect to the horizon, indicating the pitch and roll angles. By feeding the output of the INS to attitude indicators, pilots can accurately determine the aircraft's attitude and make necessary adjustments for safe and controlled flight.

The correct answer is 15 degrees per hour. Earthrate refers to the rotation of the Earth on its axis. It completes a full rotation of 360 degrees in 24 hours, which means it rotates approximately 15 degrees per hour. This rotation is responsible for the cycle of day and night on Earth.

The pin section of an AN/MS connector is normally installed on the ground side of a current. This means that the pin is connected to the part of the circuit that carries the return current back to the power source. By connecting the pin to the ground side, it helps to ensure proper grounding and electrical safety in the circuit.