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 Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 200 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 200 ΩR₂ = 200 ΩR₃ = 600 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 9 V, R₁ = 50 Ω and R₂ = 800 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 9 VR₁ = 50 ΩR₂ = 800 ΩR₃ = 500 ΩR₄ = 60 Ω

V_a = V

3.Medium

A bridge has four 500 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 25 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 500 ΩΔR = 25 Ω

V_ab = mV

4.Medium

A 220 Ω strain gauge is one arm (R₂) of a bridge with four equal 220 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 220 Ω

P_g = mW

5.Hard

A 350 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.742 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.12ΔR = 0.742 Ω

ε = µε

6.Hard

A bridge with 120 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.1 and the strain is 1200 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.1ε = 1200 µε

V_o = mV

Answer key

1. R₄ = 600 Ω
2. V_a = 8.471 V
3. V_ab = 24.39 mV
4. P_g = 10.23 mW
5. ε = 1000 µε
6. V_o = 6.3 mV

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