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

In the bridge shown, V_s = 12 V, R₁ = 20 Ω and R₂ = 250 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 20 ΩR₂ = 250 ΩR₃ = 250 ΩR₄ = 20 Ω

V_a = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 1000 Ω, R₂ = 10 Ω and R₃ = 1000 Ω. Find the unknown resistor R₄.

R₁ = 1000 ΩR₂ = 10 ΩR₃ = 1000 Ω

R₄ = Ω

3.Medium

A bridge has four 400 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 1.6 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 15 VR = 400 ΩΔR = 1.6 Ω

V_ab = mV

4.Medium

A 100 Ω strain gauge is one arm (R₂) of a bridge with four equal 100 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 100 Ω

P_g = mW

5.Hard

A strain gauge (GF = 2.1) on a member with E = 210 GPa forms a quarter bridge excited with 5 V. The output reads 2.625 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.1V_o = 2.625 mVE = 210 GPa

σ = MPa

6.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 400 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 400 µε

V_o = mV

Answer key

1. V_a = 11.11 V
2. R₄ = 10 Ω
3. V_ab = 15 mV
4. P_g = 10 mW
5. σ = 210 MPa
6. V_o = 0.5125 mV

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