Resistance Value, Forces on Strands of Wire
In physics, resistance is a characteristic of a material to oppose or resist the flow of an electrical current. The international standard measure of resistance is the ohm. In principle, it is easier to calculate the resistance of a strand of wire. Connect a battery to a wire of known voltage and compute the current passing through the wire. The electric voltage divided by the current passing through determines the wire resistance. The idea demonstrates how a multimeter measures resistance. When measuring the resistance of a material, it is important to investigate how the measured resistance is associated with the various components of the substance from which the wire is made.
The challenge of using resistance as a measurement is that it relies on the substance from which the wire is obtained as well as the geometry of the wire. The measured resistance of a wire increases when the length is increased. Similarly, decreasing the diameter of a wire increases the measured resistance. Increased levels of resistivity suggest that the material used to make the wire is very resistant to the flow of electricity. Lower levels of resistivity suggest that the substance used to make the wire transmits electrical current with ease. Resistivity is defined as the resistance in the wire multiplied by the cross-sectional area of the wire and then dividing the results the length of the wire.
Power in most households and commercial establishments is supplied in 240 volts in the form of two 120V conductors and a 120V neutral conductor. Most of the household appliances use 120 Voltage power outlets. A radio having a 120V on one of the knobs is safe to use where the power supply is of the same magnitude. It functions well without excessive heating which leads to hazards. A radio with such a voltage in the power inlet is safe to use in a hospital room as well as in the bedroom because it is within the acceptable voltage domain.
Stranded wires are used to transmit high voltage power to different locations because of their flexibility compared to solid wires. Stranded wire is made up of small wires bundled together to form a larger power conductor. Stranded wire will be more flexible and adapted than a solid ire of the same cross-sectional area. A stranded wire works best in situations where higher resistance to metal fatigue is of importance. A typical example of this application is the connection between circuit boards in a multi-printed circuit where the rigidity of block wire might result to production of much stress due to movement when being assembled or repaired.
For high frequencies in the transmission lines, current flows close to the surface of the wire due to skin effect that causes increased power loss in the wire an effect that is resolved using stranded wire. The surface area in a stranded wire is greater than that of solid wires which helps to reduce power loss during transmission. For most of the high voltage applications, the proximity effects are more pronounced than skin effect. A Simple stranded wire helps to reduce the proximity effects. Litz wire that has individual strands twisted in a specified pattern help to reduce the forces in the power supply lines. A change in the flow direction may have adverse effects on a high voltage power supply system.