Question

Bonding element in a strain gauge must have
Option-
A.Zero insulation resistance
B.Low insulation resistance
C.High insulation resistance
D.Infinite insulation resistance

Answer 1

Strain gauge is an example of an electrical sensor which is used to determine the magnitude of force applied or strain. When different intensity of force is applied to gauge its resistance changes which further changes the net output of electric current.

Complete answer:
The value of insulation resistance is measured in terms of ohms. Insulation resistance is calculated for electrical wires, cables and other electric equipment. Insulation resistance is used in electrical devices to protect the device from accidental electrical discharge.
A bonding element of strain gauge is generally an element wire which is insulated so that its value does not deflect by the influence of other factors.
The value of insulation resistance may vary under the influence of various factors like humidity, temperature, and environmental factors. Change in insulation resistance due to these factors give false readings of strain produced in the bonding element of gauge strain. As a result, the strain gauge is not capable of protecting our electrical appliances.
Very high value of insulation resistance indicates that a very large amount of current is passed through the insulation resistance and leaves a very minute amount of current to escape through it. Therefore, insulation resistance ensures the full safety of electrical devices and avoids the chances of accidental electrical discharge.
$\Rightarrow$ Bonding element in a strain gauge must have High insulation resistance.

Therefore, option $\left( C \right)$ is the correct option.

Note:
Strain gauge is also used to determine pressure, tension and weight. There is a particular range of insulation resistance which is $1M\Omega$ for $1,000$ volts. Basic method of calculating insulation resistance is by applying ohm’s law.