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 = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 50 ΩR₂ = 300 ΩR₃ = 400 ΩR₄ = 300 Ω

I_s = mA

2.Easy

In the bridge shown, V_s = 3 V, R₁ = 80 Ω and R₂ = 1000 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 3 VR₁ = 80 ΩR₂ = 1000 ΩR₃ = 500 ΩR₄ = 1000 Ω

V_a = V

3.Medium

A bridge with four 220 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 182.9 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 220 ΩV_ab = 182.9 mV

ΔR = Ω

4.Medium

A bridge has four 300 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 1.5 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 5 VR = 300 ΩΔR = 1.5 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.1 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.1ε = 800 µε

V_o = mV

6.Hard

A 120 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.252 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.1ΔR = 0.252 Ω

ε = µε

Answer key

1. I_s = 12.86 mA
2. V_a = 2.778 V
3. ΔR = 11 Ω
4. V_ab = 6.25 mV
5. V_o = 4.2 mV
6. ε = 1000 µε

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