(b) In a strain gauge, the increase in resistance ΔR depends on the increase in length ΔL.
The variation of ΔR with ΔL is shown in Fig. 7.1.

8
ΔR/Ω

6+

4

2-

0
0

2

4

6

8

10

ΔL/10⁻⁵ m

Fig. 7.1

The strain gauge is connected into a circuit incorporating an ideal operational amplifier (op-amp), as shown in Fig. 7.2.

+6.00 VO

strain
gauge

+5 V

+2.00 V

OVO

153.0 Ω

A

+

-5 V

X

Y

Fig. 7.2

This question tests Deformation of solids in A-Level Physics (syllabus code 9702). It is worth 10 marks.

This question appeared in the Cambridge A-Level Physics Feb/Mar 2017 examination, Paper 4 Variant 2 (9702_m17_qp_42.pdf).

Question

(b) In a strain gauge, the increase in resistance ΔR depends on the increase in length ΔL.
The variation of ΔR with ΔL is shown in Fig. 7.1.

8
ΔR/Ω

6+

4

2-

0
0

2

4

6

8

10

ΔL/10⁻⁵ m

Fig. 7.1

The strain gauge is connected into a circuit incorporating an ideal operational amplifier (op-amp), as shown in Fig. 7.2.

+6.00 VO

strain
gauge

+5 V

+2.00 V

OVO

153.0 Ω

A

+

-5 V

X

Y

Fig. 7.2

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