The resistors are generally made of thin wires of Eureka or Manganin while the wires used in connections are comparatively thicker and are of copper or aluminum. Why?
on resistors you need a higher values like 1 mega-ohms or more ...they made of thin carbon film... on wiring you do not like to have resistance on wires ..because of dropping voltage on them due to passing current through them... so they are copper and thicker ( minimum resistance )... on stretching the wire ...length doubles and cross section area will be a half so resistance will increase by four ....
The resistors are generally made of thin wires of Eureka or Manganin while the wires used in connections are comparatively thicker and are of copper or aluminum. Why?
on resistors you need a higher values like 1 mega-ohms or more ...they made of thin carbon film... on wiring you do not like to have resistance on wires ..because of dropping voltage on them due to passing current through them... so they are copper and thicker ( minimum resistance )... on stretching the wire ...length doubles and cross section area will be a half so resistance will increase by four ....
Constantan , also known as Eureka, is an alloy of copper and nickel , was discovered in 1887 , and has been used for resistance all along, apart from other applications.Its preference for resistance wire stems from high resistivity, low temperature coefficient of resistance, ability to attain good resistance values in small size, stability, ability to draw in thin wires. It's melting point is also high at over 1200 degrees Celsius.Apart from resistance, constantan is also used in thermocouples.Manganin is an improvement over constantan, discovered in 1892. It is an alloy of copper , manganese and nickel. Its temperature coefficient of resistance is near zero, and this makes it ideal for ammeter shunt, and high precision resistance.Manganin is used in resistance standards, its melting point is around 1000 degrees Celsius, and maximum usage temperature is limited to 300 degrees Celsius.
We know that,Since the length and resistance are equal, resistivity(rho) is directly proportional to area of cross section(A).Copper—1.72x10–8 ohm-m.Manganin—48.2x10–8 ohm-m.→Copper has less resistivity than Manganin. As resistivity is directly proportional to area of cross section, Copper has less area of cross scetion than manganin.→Hence, Copper wire is thinner than manganin wire.
Look at the resistivity of different materialsNichrome has more resistivity than copper. Hence for equal length and resistance it has to to be thicker since resistance is inversely proportional to the diameter of the wire.