Enter COhm's Law & Circuit Mathategory Name
If a 24-volt aircraft electrical circuit has a measured resistance of 6 ohms, this is the amount of current flowing through the circuit.
4 amperes
Using Ohm's Law (I = V / R), dividing 24 volts by 6 ohms results in 4 amperes of current.
This common circuit protection device is designed to open and interrupt current flow when excessive electrical draw causes an internal metal strip to melt.
Fuse
A fuse relies on a calibrated metallic link that melts and opens the circuit permanently when subjected to overcurrent conditions.
The nominal open-circuit voltage rating of a single fully charged lead-acid storage battery cell is approximately this value.
2.1 volts
A standard lead-acid cell provides roughly 2.1 volts open circuit, which sums to 12.6 volts for a 6-cell 12V battery or 25.2 volts for a 12-cell 24V battery.
As the numerical American Wire Gauge (AWG) size designation of an aircraft electrical wire decreases, this physical attribute of the wire increases.
Cross-sectional area and current-carrying capacity
A lower AWG number (e.g., AWG 2 vs. AWG 20) means a thicker wire with a larger cross-sectional area and a higher ampacity rating.
The core mechanical difference between a traditional direct-current (DC) generator and a standard aircraft alternator is that the generator utilizes a mechanical commutator, whereas the alternator uses these components.
Slip rings and rectifier diodes
Alternators produce AC internally and route it through continuous slip rings and solid-state diode rectifiers to output DC power.
This is the total power consumed by a 24-volt DC aircraft bus when it draws a continuous current of 5 amperes.
120 watts
Electric power in watts is calculated using Joule's Law: P = V × I (24 V × 5 A = 120 W).
This semiconductor component allows current to flow freely in one forward direction while virtually blocking it in the reverse direction.
Diode
A semiconductor diode permits forward-biased current flow and blocks reverse-biased current flow.
This specialized diagnostic instrument is used to check the specific gravity of the liquid electrolyte within a traditional lead-acid storage battery cell.
Hydrometer
A hydrometer measures electrolyte density compared to water, directly indicating the concentration of sulfuric acid and the state of charge.
According to FAA AC 43.13-1B, this termination method is strongly preferred over soldering for aircraft electrical wire splices and terminals due to superior resistance to vibration fracture.
Crimp connection
Crimp connections deform the terminal barrel evenly around the strands, avoiding rigid solder wicking points that fail under airframe vibration.
Most traditional aircraft electric starter motors use this specific type of internal electrical winding configuration because it provides high starting torque at low rotational speeds.
Series-wound motor
Series-wound DC motors pass armature current directly through the field coils in series, producing maximum torque when current draw is highest at startup.
Three individual resistors with values of 2 ohms, 3 ohms, and 5 ohms are connected in series within a 24-volt circuit. This represents their total equivalent resistance.
10 ohms
In a series circuit, individual resistances are added directly together (\(R_t = R_1 + R_2 + R_3 = 2 + 3 + 5 = 10\text{ ohms}\)).
This electrically operated switch uses a low-control current coil to close a heavy-duty contact path, frequently utilizing a movable magnetic plunger to engage high-draw devices like starter motors.
Solenoid
A solenoid incorporates an electromagnetic coil and a sliding plunger mechanism to handle heavy mechanical engagement and high-current closing.
This dangerous self-accelerating failure mode in nickel-cadmium batteries occurs when internal resistance drops, causing excessive current generation and severe heat buildup that can ruin the cells.
Thermal runaway
Thermal runaway in Ni-Cad batteries is a destructive positive feedback loop where high temperature lowers internal resistance, increasing charging current and further raising temperature.
When multiple current-carrying electrical wires are bundled together in a single harness, their maximum allowable current ratings must be adjusted downward via this practice to prevent overheating.
Derating
Derating reduces the maximum permitted current in bundled wires because adjacent heat sources restrict thermal dissipation.
The output voltage of a traditional aircraft DC generator is regulated by varying the amount of electrical current passing through this specific internal component.
Field winding
By altering the current through the field frame windings via a voltage regulator, the magnetic field strength changes, which directly governs generator output voltage.
Two identical resistors, each rated at 20 ohms, are connected in a parallel branch configuration. This is their total combined resistance.
10 ohms
For two equal resistors in parallel, the total resistance is half the value of one resistor (20 / 2 = 10 ohms).
This passive component stores electrical energy electrostatically in an internal electric field and is heavily used in avionics power filters to smooth out voltage spikes.
Capacitor
Capacitors store energy in an electric field between conductive plates separated by a dielectric material.
During the overcharging process of a lead-acid storage battery, the electrolyte actively decomposes and emits this highly flammable and explosive combination of gases.
Hydrogen and oxygen
Electrolysis of water during overcharging breaks down H₂O into free hydrogen (H₂) and oxygen (O₂) gases, creating an extreme explosion hazard.
This braided metallic outer layer applied over insulated aircraft wiring or bundles is used primarily to block electromagnetic interference (EMI) from disrupting sensitive avionics.
Shielding braid
A metallic shielding braid acts as a Faraday cage around the inner conductor(s), routing external high-frequency interference safely to airframe ground.
This modern type of aircraft AC generator eliminates rotating mechanical brushes and commutators entirely by inducing current magnetically into the main rotor.
Brushless alternator
A brushless alternator uses a small permanent magnet generator (PMG) and exciter winding configuration on the same shaft, eliminating carbon dust and wear.
According to standard FAA installation practices, the maximum allowable voltage drop for a continuous-operation electrical power line in a 28-volt system should not exceed this percentage of the source voltage.
3 percent
Standard FAA guidelines (such as AC 43.13-1B) specify a 3% voltage drop limit for continuous operation circuits and 7% for intermittent operation circuits.
This specialized diode is specifically designed to operate stably in its reverse-bias breakdown region without destruction, making it ideal for voltage reference and regulation tasks.
Zener diode
A Zener diode is engineered to allow current to flow in the reverse direction when a specific breakdown voltage (Zener voltage) is reached, providing a steady reference voltage.
A nickel-cadmium battery cell that reads zero or extremely low voltage while the rest of the pack is healthy likely requires this specific maintenance procedure to correct "cell imbalance."
Equalization (Deep cycling)
Discharging individual Ni-Cad cells completely to zero volts and shorting them with resistor clips before a controlled constant-current recharge re-aligns cell capacities.
For intermittent operation electrical circuits in a 28-volt aircraft installation, the maximum allowable voltage drop between the main bus and the driven component is typically limited to this percentage.
7 percent
Intermittent loads (such as landing gear actuators or cowl flaps) operate for short intervals, permitting a higher design voltage drop limit of 7% per FAA recommendations.
This specific electromagnetic relay unit prevents the aircraft storage battery from discharging backward through a DC generator when the engine slows down or generator output drops below system voltage.
Reverse-current cutout relay
The reverse-current cutout relay uses a voltage and current coil to automatically close the main generator contactor when generator voltage exceeds battery voltage, and opens it when current tries to flow backward.