The electrical systems within an aircraft are extensive. Steps need to be taken to ensure that the system doesn’t overload causing a power outage on an aircraft. Resistors are electrical components that oppose the flow of electrical current. They are by nature, passive components that only reduce voltage rather than increase them. Wirewound resistors are cylindrical components with resistive wire wrapped around them. The rod is typically made of ceramic or fiberglass and the wire is usually made out of an alloy such as nichrome. An exterior casing insulates the wirewound resistors to help block any heat coming from the circuit interruption.
The key to wire wound resistors is in the winding and the material of the wire. The level of resistance can be changed by adjusting the wire resistivity and wire length. A metal wire with high resistance opposes large amounts of electric current, while, a metal wire with low resistance blocks a small amount of electric current. The longer the wire, the more space the free electrons have to travel and collide with atoms, therefore the higher the resistance. During collision, energy is lost in the form of heat and only a small amount of electric current flows through the wire resistor. In comparison, electrons only have to travel a short distance, thus do not collide with atoms as frequently. The result is that a larger amount of electricity passes through the resistor. In a similar principle to the length of the wire, the size of the wire coil spiral directly affects the level of resistance. If the cross section of the coil is small, the electrons are more compact, so collide with the atoms, thus losing energy. If the coil is larger, the resistance is lower as more electrons escape collision and carry on through the resistor.
Two types of wire resistors are commonly used with aircraft equipment. Precision wire resistors are used for low temperature applications that require a high level of accuracy for example calibration equipment. Power wire resistors are used in instances of high temperature. In an aircraft, a power resistor can be found in the main electrical system as a current sensor. Due to their adaptability, wire resistors are a popular hardware component to use in aircraft. They can be manufactured in all different sizes and materials to suit the desired task. Compared to other resistors, wire resistors are low cost, have high accuracy and stability rates, and offer wide variances in resistance. The downfall of wire resistors is that, under high frequencies, the wire acts as an inductor.
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