Why to measure the resistivity of resistance wire and why to use current limiting

Why to measure the resistivity of resistance wire and why to use current limiting

When the maximum resistance of the sliding rheostat is 2-5 times of the resistance of the measuring resistance wire, the current limiting circuit is used, so the circuit is simple and energy saving, so the current limiting circuit is commonly used to measure the resistance of the resistance wire

Double arm bridge experiment: measuring resistance and resistivity. Why should the ratio knob RS be set as small as possible?
Why is it necessary to set the ratio knob RS as small as possible in measurement? Why is it not allowed to set RN to "0" in measurement?

It is beneficial to start to adjust to the minimum or maximum gear. In the actual test, it is found that even if the pointer of the same type of bridge has different deflection, it should have been determined that the resistance of the tested object can be measured with the bridge when it has decided to use the double arm bridge, and it will not exceed the range, When the minimum range is selected, we can know the pointer deflection when the reading is less than the real value. Knowing and remembering this is very helpful for the subsequent operation. The back and forth adjustment often results in the loss of time. It is troublesome for the temperature rise test and other tests requiring time limit measurement results. The good use of double arm bridge is to measure the resistance value in the shortest time, To be quick, you need to reduce the number of back and forth, have a clear mind, and respond accurately. A larger current can make the reading more accurate, because the double arm bridge is originally used to measure small resistance