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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 10 V.

V_s = 10 VR₁ = 600 ΩR₂ = 400 ΩR₃ = 20 ΩR₄ = 40 Ω

V_ab = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 120 Ω and R₃ = 200 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 120 ΩR₃ = 200 Ω

R₄ = Ω

3.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 5 VR₁ = 120 ΩR₂ = 50 ΩR₃ = 40 ΩR₄ = 1000 Ω

R_th = Ω

4.Medium

A 200 Ω strain gauge is one arm (R₂) of a bridge with four equal 200 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 = 200 Ω

P_g = mW

5.Hard

A bridge with 1000 Ω arms is excited with 2.5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.12 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.12ε = 750 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 0.063 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.1ΔR = 0.063 Ω

ε = µε

Answer key

1. V_ab = −2.667 V
2. R₄ = 1200 Ω
3. R_th = 73.76 Ω
4. P_g = 11.25 mW
5. V_o = 1.988 mV
6. ε = 250 µε

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