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as its temperature-sensing element. The resistance bulb contains a length of small diameter nickel wire,
wound on a mica form and enclosed in a thin stainless steel tube. The resistance of the nickel wire increases
as its temperature increases.
The resistance bulb is installed in a Wheatstone bridge circuit in such a way that current flowing
through the indicating instrument changes as the resistance of the bulb changes.
resistance welding. A form of electrical welding used for joining thin sheets of metal. The metal to be
welded is pressed together by the electrodes of the welding machine, and low-voltage current is passed
through the metal.
Heat caused by the current softens the metal, and pressure on the electrodes forces the softened
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 486
metal together. The current is stopped, but the pressure is held on the electrodes until the softened metal
hardens. Spot welding and seam welding are types of resistance welding.
resistance wire. Wire made of such alloys as Manganin or Nichrome. This wire has a high resistance and
is used to make precision, wire-wound resistors and electric heater elements.
resistive circuit (electrical circuit). An electrical circuit in which all of the opposition to the flow of
electrons is caused by circuit resistance. In a resistive circuit, the current and voltage are in phase.
resistivity (electrical characteristic). The amount of resistance for a given volume of material or for a
given amount of surface area. Resistivity is the reciprocal (the opposite) of conductivity.
resistor (electrical component). A component used to place a specific amount of resistance in an electrical
circuit.
resistor color code. A color code used to show the amount of resistance and the resistance tolerance of a
composition resistor. Three or four colored bands are placed around one end of the resistor. The band
nearest the end of the resistor indicates the first significant digit in the resistance. The second band is for
the second significant digit. The third band shows the number of zeros to add to the two significant digits.
The fourth band shows the tolerance of the resistance in percentage of the nominal value. The colors and
their meanings are:
resistor spark plug (ignition system component). A shielded aircraft spark plug with a built-in carbon
resistor between its terminal end and center electrode. Shielded ignition leads have a metal braid around the
insulator, and this braid, with the insulator and conductor, acts as a capacitor and stores electrical energy.
When the spark jumps the gap in the spark plug, the energy stored in the lead capacity causes the
spark to continue after the fuel is ignited. This prolonged spark needlessly wears away the spark plug
electrodes. The built-in resistor causes enough opposition to this current to reduce the spark duration and
increase the life of the spark plug electrodes.
resolution (radar technology). The ability of radar to show discrete targets separately. The better the
resolution, the closer two targets can be to each other and still be detected as separate targets.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 487
resolution advisory (air traffic control). A display indication given to the pilot by the traffic alert and
collision avoidance system (TCAS II) recommending a maneuver to increase vertical separation relative to
an intruding aircraft.
Positive, negative, and vertical speed limit advisories constitute the resolution advisories. A
resolution advisory is also classified as corrective or preventive.
resonance (electrical). The condition in an electrical circuit in which the inductive reactance and the
capacitive reactance are equal. The reactances are determined by the frequency, and a circuit is resonant for
a very narrow band of frequencies.
resonance (mechanical). The frequency of vibration of a mechanical system or device at which the
vibration has the greatest displacement. The physical dimensions of an object determine the frequency at
which it is resonant.
resonance method of ultrasonic inspection. A method of nondestructive inspection for internal faults in a
piece of material. A pulse of ultrasonic energy of known frequency and intensity is induced into the
material, and the vibration produced by this energy is displayed on an oscilloscope. There is a definite
change in the vibration pattern if the wave of energy passes over a fault within the material.
resonant circuit (electrical circuit). A tuned electrical circuit that contains both capacitance and
inductance. By adjusting the amount of capacitance or inductance, the circuit can be tuned (its resonant
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航空术语词典Dictionary of Aeronautical Terms 下(24)