Rheostats: Mijell, Bina û Têkçûna Karên yênwendekariyê

Electrical4u

qalab: بەشی بنەڕەتی برق

China

Rheostat dike nav bûyeke ye ku dike bûyekê vebend ku dikare biguheztine baranî an voltage di cirkewtên baranî de. Rheostats ziyade ji bo devên kontrolê nivînê bikar hin, wek kontrolkirina çepê motorê baranî, dengê rojikê an derexa fûrnê baranî. Rheostats da heta bikar ne biçavên jêrîne voltageyan an potential differences nayê yên dike bibalane me voltageyan an potential differences yê xas.

Çi ye Rheostat?

Rheostat dike nav divice ye ku dikare biguheztine resistance di cirkewtên baranî de bi guheztin pozisyonê contact point ê ser elementê resistive.

Elementê resistive dikare be sîm metal, rod karbon, an solution liquid. Contact point dikare be terminal sliding, knob rotating, an wiper arm.

Resistanceya rheostatê dipencet lê length û cross-sectional area ya elementê resistive, an materialê ku hejir in. Resistanceya dikare hatî hesab kirin bi karibandina formula:

ku R resistance ye, ρ resistivity ya material, l length ya elementê resistive, an A cross-sectional area.

Baranî yên di rheostat de dikare control bike bi serkeftin contact point ê tuwer û derbas rawe endeya elementê resistive. Ji tuwer contact point ê be endeya, resistanceya kehater û baranîya berzher. Ji derbas contact point ê be endeya, resistanceya berzher û baranîya kehater.

Çimîna Rheostats Construction?

Rheostats dikarin construction bike bi şêwek different depending li applications û specifications. Some common types of rheostats are:

Wire-wound rheostats: Wan dikarin jêbirin bi pêşandina wire long ê material high-resistivity ser core insulating, wek ceramic an plastic.
Wire dikare coiled be spiral an helical shape. Sliding terminal an rotating knob dikare move along wire bi guheztin resistance. Wire-wound rheostats suitable for high currents and low voltages.
Carbon rheostats: Wan dikarin jêbirin bi karibandin carbon rod an plate as element resistive. Wiper arm dikare move along surface carbon bi guheztin resistance. Carbon rheostats suitable for low currents and high voltages.
Liquid rheostats: Wan dikarin jêbirin bi karibandin solution conducting liquid, wek salt water an acid, as element resistive. Two electrodes immersed in liquid and connected to power source and load. Distance between electrodes can vary to change resistance. Liquid rheostats suitable for very high currents and low voltages.

Çi Materials Bikar Hin bo Rheostats?

Materials bikar hin bo rheostats divê high resistivity, high working temperature, high corrosion resistance, suitable mechanical strength, suitable ductility, an low cost. Some common materials used for rheostats are:

Platinum: Platinum noble metal ye ku high resistivity û melting point high e. Also has high resistance to oxidation, high ductility, high malleability, good mechanical strength, an good stability with temperature and mechanical stress. But platinum expensive û scarce, so use in electrical engineering limited to laboratory furnaces, resistance thermometers, an some rheostats.
Constantan: Constantan copper-nickel alloy ye ku low-temperature coefficient of resistance, meaning resistivity constant over wide range of temperatures. Also has high resistance to oxidation, good mechanical strength, an good stability with temperature and mechanical stress. Constantan widely used for electrical connections in instruments, such as shunt resistors, series resistors, swamp resistors, standard resistors, an rheostats.
Nichrome: Nichrome nickel-chromium alloy ye ku high resistivity û melting points. Also has high resistance to oxidation and corrosion, good mechanical strength, an good ductility. Nichrome widely used for heating elements and wire-wound rheostats.

Çi Applications of Rheostats?

Rheostats many applications in various fields of engineering and science. Some examples are:

Power control: Rheostats can be used to control the power output of devices such as electric motors, lights, ovens, furnaces, etc. By varying the resistance of a rheostat in series with a device, the voltage or current supplied to it can be adjusted.
Voltage divider: Rheostats can be used to divide a voltage source into smaller fractions by connecting them in series with each other. By varying the resistance of one or more rheostats in a voltage divider circuit, different output voltages can be obtained.
Potentiometer: Rheostats can be used to measure an unknown voltage or potential difference by balancing it with a known one. A potentiometer is a type of rheostat that has three terminals: one connected to a fixed end of the resistive element, one connected to a variable contact point along it, and one connected to an external circuit. By adjusting the position of the contact point until no current flows through it (i.e., when both voltages are equal), the unknown voltage can be determined.
Strain gauge: Rheostats can be used to measure strain (i.e., deformation) in materials by changing their resistance when subjected to stress (i.e., force). A strain gauge is a type of rheostat that has two terminals connected to opposite ends of a thin metal foil that is attached to an object under stress. As the object deforms due to stress, so does the foil; this changes its length and cross-sectional area (and hence its resistance). By measuring this change in resistance using an electrical circuit (such as the Wheatstone bridge), strain can be calculated.