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 = 12 V.

V_s = 12 VR₁ = 500 ΩR₂ = 300 ΩR₃ = 250 ΩR₄ = 60 Ω

V_ab = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 150 Ω and R₃ = 250 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 150 ΩR₃ = 250 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 = 6 VR₁ = 200 ΩR₂ = 60 ΩR₃ = 500 ΩR₄ = 1000 Ω

R_th = Ω

4.Medium

A 150 Ω strain gauge is one arm (R₂) of a bridge with four equal 150 Ω arms and an excitation of 6 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 6 VR = 150 Ω

P_g = mW

5.Hard

A bridge with 120 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.1 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.1ε = 750 µε

V_o = mV

6.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.175 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.175 Ω

ε = µε

Answer key

1. V_ab = 2.177 V
2. R₄ = 1875 Ω
3. R_th = 379.5 Ω
4. P_g = 60 mW
5. V_o = 4.725 mV
6. ε = 250 µε

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