Free NCATT AET Exam Flashcards

Ohm's Law states that current equals voltage divided by resistance: I = E/R. Increasing voltage raises current, while increasing resistance lowers current when the other quantity is unchanged.

Power is the rate of electrical work and is measured in watts. Use P = E × I; Ohm's Law also gives P = I²R or P = E²/R.

A series circuit has one current path, so the same current passes through every component. Individual resistance values add, and the source voltage divides among the loads.

Parallel branches share the same voltage but divide current among multiple paths. Their equivalent resistance is always less than the smallest individual branch resistance.

The algebraic sum of all voltage rises and drops around a closed loop is zero. Equivalently, the component voltage drops equal the applied source voltage.

The algebraic sum of currents at a junction is zero: total current entering the junction equals total current leaving it. Charge does not accumulate at the node.

Inspect first, then use voltage or current measurements only on an energized circuit when required. De-energize and isolate power before resistance or continuity tests because an ohmmeter supplies its own test current.

Connect a voltmeter in parallel across the measured points. Connect an ammeter in series so load current passes through it; placing an ammeter across a source can create a short.

Frequency is the number of complete cycles per second, measured in hertz. Period is the duration of one cycle, and the two are reciprocals: T = 1/f.

RMS is the effective AC value that produces the same heating as an equal DC value. For a sine wave, RMS equals approximately 0.707 times peak value.

In a purely inductive AC circuit, voltage E leads current I. Inductive reactance increases with both frequency and inductance: XL = 2πfL.

In a purely capacitive AC circuit, current I leads voltage E. Capacitive reactance decreases as frequency or capacitance increases: XC = 1/(2πfC).

Resonance occurs when inductive and capacitive reactance are equal, XL = XC. Their opposing effects cancel, leaving a series RLC circuit with minimum impedance determined by resistance.

True power is measured in watts; apparent power is RMS volts times RMS amperes in VA. Power factor is true power divided by apparent power and equals 1 for a purely resistive load.

The bands identify significant digits, a multiplier, and tolerance. Read them in the specified order to determine resistance, then confirm suspect or illegible components with an ohmmeter.

Other circuit paths can appear in parallel and make an in-circuit resistance reading falsely low. Isolating one lead lets the ohmmeter measure the component rather than the surrounding network.

An open winding has no continuous path between its leads, so an ohmmeter indicates very high or infinite resistance. The coil cannot carry its intended current.

An open capacitor cannot charge or pass the expected changing signal; a shorted capacitor presents very low resistance and may draw excessive current. De-energize and discharge it before resistance or capacitance tests.

More secondary turns than primary turns produce a step-up in voltage and a corresponding current decrease. Fewer secondary turns produce a voltage step-down and current increase.

After confirming correct primary input, zero secondary output can indicate an open winding, a shorted winding, or another loss of coupling. De-energize before resistance checks.

Contact names describe the de-energized state. Energizing the relay coil closes normally open contacts and opens normally closed contacts, allowing a low-current control circuit to switch another circuit.

Energizing its coil creates a magnetic field that moves an iron core or plunger. This converts electrical control into linear mechanical motion.

A diode conducts primarily in one direction and blocks the opposite polarity. Arrangements such as a four-diode bridge use that behavior to convert both AC half-cycles into pulsating DC.

Active filters use powered components and can provide gain; passive filters do not. Low-pass and high-pass select below or above cutoff, while band-pass selects a range and band-stop rejects one.

An amplifier restores energy lost in the circuit, while regenerative positive feedback returns an in-phase portion of output to the input. A frequency-selective network sets the operating frequency.

Astable circuits free-run between two temporary states, monostable circuits produce one timed pulse after a trigger, and bistable circuits retain either of two stable states.

A limiter prevents a signal from exceeding selected positive, negative, or dual thresholds. Diode orientation and any applied bias determine where the waveform is clipped.

Each octal digit represents a three-bit group, while each hexadecimal digit represents a four-bit group. Grouping from the radix point makes conversion systematic.

AND requires all inputs high; OR requires at least one high input; XOR requires unlike inputs in the two-input case. Their truth tables define the exact behavior.

NOT inverts one input. NAND is an AND result followed by inversion, and NOR is an OR result followed by inversion; NAND and NOR can each implement other logic functions.

A flip-flop stores one binary state. Connected flip-flops can count input pulses, and decoder circuitry converts the stored count into segment signals for a numeric display.

De-energize the source as quickly and safely as possible before touching the victim. Use approved isolation procedures, then begin appropriate first aid and summon emergency help.

These electromagnetic energy sources can expose personnel even without direct conductor contact. Identify the source, control access and energy, and use the required procedures and protective equipment.

A Safety Data Sheet identifies a chemical's hazards, handling and storage controls, required protective equipment, and emergency response. Technicians consult it before using an unfamiliar hazardous material.

It removes debris as work proceeds, accounts for tools and materials, and prevents dropped or forgotten objects from remaining near aircraft systems where they could cause damage.

An Airworthiness Directive is a mandatory regulatory action. A manufacturer's service bulletin is generally advisory unless an AD or another applicable requirement makes its instructions mandatory.

Use current manufacturer instructions when they cover the task. AC 43.13 provides acceptable methods when specific instructions are absent and its conditions for use are satisfied.

The correct tool protects the hardware, aircraft, and technician. Use calibrated precision or torque tools when specified, and never substitute a tool for a purpose it was not designed to perform.

A grounded work surface, personnel grounding, careful handling, and protective packaging equalize charge and control discharge paths before static energy can damage a circuit or component.

Galvanic corrosion requires dissimilar metals in electrical contact and an electrolyte. Control it with approved isolation between metals, sealants or finishes, moisture control, proper storage, and good housekeeping.

Safety wire restrains a fastener or connector against vibration-induced loosening. Route and tension it so the wire tends to hold the secured item in the tightening direction.

Coaxial cable protects RF signal paths, twisted pairs reduce induced interference in balanced circuits, and single-conductor wiring uses the bonded aircraft structure as the return path.

American Wire Gauge uses an inverse scale: a larger AWG number means a smaller conductor diameter. Selection must also account for current, voltage drop, temperature, routing, and mechanical protection.

It can verify a complete path and help locate an open conductor, switch, fuse, lamp, or connection. Isolate the circuit enough to prevent parallel paths from masking the fault.

An open breaks the intended current path. A short creates an unintended low-resistance path, often causing excessive current; ground faults are shorts to structure or another return path.

Meters are part of the circuit during measurement. A high-impedance voltmeter minimizes parallel loading, while an ammeter's low resistance requires a correct series connection and range.

An oscilloscope displays voltage versus time, revealing waveform shape, peak-to-peak amplitude, period, frequency, timing, and phase relationships that an averaged numeric reading can hide.

Roll is motion about the longitudinal axis and is controlled by ailerons; pitch is about the lateral axis with elevators; yaw is about the vertical axis with the rudder.

Lift balances weight and thrust balances drag. A disturbance to either pair produces acceleration until the forces balance again or the aircraft establishes a new flight condition.

The cockpit person can operate the brakes if the tow bar fails or another emergency develops. The towing team must follow aircraft-specific instructions, communicate clearly, and maintain clearance.