Question

The strain gauge is not bonded to the specimen.
(A) True
(B) False

Answer 1

Hint
From the definition of strain gauge we know that a strain gauge is a device that uses the physical property of electrical conductance to measure the strain of an object. So from this definition of the strain gauge we can see whether it needs to be bonded to the specimen.

Complete Step by Step Solution
When any kind of physical force is applied on an object, it increases the stress or strain of that object. The stress is an object’s internal revisiting force and the strain is the deformation or the displacement that occurs in the body. A Strain gauge is a sensor whose resistance varies with the force applied on it. It works by changing the force or pressure into a change in electrical resistance which can be measured after that. When an electrical conductor is stretched, it becomes longer and narrower and as a result the end-to-end resistance increases. And when a conductor is compressed, it broadens and shortens and as a result, the end to end resistance decreases. Thus a strain gauge is used to pick up the expansion as well as the contraction. Therefore to measure the strain of any object or specimen, the material in the strain gauge needs to go through that same strain as that object.
To do so, therefore the strain gauge has to be under the same force as the specimen and thus need to be attached to the body of the specimen. Therefore, the strain gauge is bonded to the specimen.
So the answer to this question will be false.
Hence, the correct option is (B).

Additional Information
The strain gauge works on the principle of variation of resistance as a function of strain. The strain gauges are usually attached to the substance with the use of special glue, and the type of the glue used normally depends on the length of time for which the gauge needs to be attached to the substance. If it is needed to be attached for a small period up to a few weeks, then cyanoacrylate glue is used. And if it is for a longer period, then epoxy glue is used.

Note
The three main types of strain gauge configurations are the quarter-bridge, half-bridge, and full-bridge and they are determined by the number of active elements in the Wheatstone bridge, the orientation of the strain gauges, and the type of strain being measured. In practice, the strain gauges are commonly used to manufacture pressure sensors and are commonly made out of silicon, polysilicon, thick film, metal film, etc.