Question

In the context of low resistances, identify the INCORRECT statement

• A. standard low resistances have four terminal construction.
  
• B. Kelvin bridge is used for measuring low resistance, precision depends on the detector sensitivity.
• C. A pair of ratio arms in Kelvin bridge for measuring the low resistance eliminates the error due to thermo emf.
• D. low resistances used for ammeter shunts are usually made with a suitable number of plates of large area and all the plates connected in parallel.

Answer 1

The correct option is C A pair of ratio arms in Kelvin bridge for measuring the low resistance eliminates the error due to thermo emf.

(i) Low resistance has four terminals to remove effect of lead resistance.

(ii) Kelvin double bridge is used to measure low resistance whose precision depends on the detector sensitivity.

(iii) Pair of ratio arms in Kelvin bridge for measuring the low resistance eliminates error due to lead resistance.

Note:
Low resistance $\to$ Four terminal to remove effect to lead resistance

Medium resistance $\to$ Two terminals

High resistance $\to$ Three terminals to remove insulation resistance.