Wheatstone bridge & strain gauges worksheet with answers

Free printable Wheatstone bridge & strain gauges worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

The bridge shown is supplied with V_s = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 400 ΩR₂ = 300 ΩR₃ = 50 ΩR₄ = 200 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 2 V, R₁ = 200 Ω and R₂ = 40 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 200 ΩR₂ = 40 ΩR₃ = 40 ΩR₄ = 40 Ω

V_a = V

3.Medium

A bridge has four 350 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 1.4 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 350 ΩΔR = 1.4 Ω

V_ab = mV

4.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 20 ΩR₂ = 800 ΩR₃ = 50 ΩR₄ = 40 ΩR_g = 200 Ω

I_g = µA

5.Hard

A strain gauge (GF = 2) on a member with E = 110 GPa forms a quarter bridge excited with 5 V. The output reads 1.25 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2V_o = 1.25 mVE = 110 GPa

σ = MPa

6.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 200 µε

V_o = mV

Answer key

1. I_s = 65.14 mA
2. V_a = 0.3333 V
3. V_ab = 6 mV
4. I_g = 32960 µA
5. σ = 55 MPa
6. V_o = 0.3 mV

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