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 = 1000 Ω, R₂ = 50 Ω and R₃ = 50 Ω. Find the unknown resistor R₄.

R₁ = 1000 ΩR₂ = 50 ΩR₃ = 50 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 2 V, R₁ = 300 Ω and R₂ = 100 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 300 ΩR₂ = 100 ΩR₃ = 1000 ΩR₄ = 50 Ω

V_a = V

3.Medium

A 150 Ω strain gauge is one arm (R₂) of a bridge with four equal 150 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 150 Ω

P_g = mW

4.Medium

A bridge has four 330 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 33 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 330 ΩΔR = 33 Ω

V_ab = mV

5.Hard

A bridge with 120 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.12 and the strain is 1200 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.12ε = 1200 µε

V_o = mV

6.Hard

A 120 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.0636 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.12ΔR = 0.0636 Ω

ε = µε

Answer key

1. R₄ = 2.5 Ω
2. V_a = 0.5 V
3. P_g = 41.67 mW
4. V_ab = 47.62 mV
5. V_o = 3.18 mV
6. ε = 250 µε

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