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 = 50 Ω, R₂ = 40 Ω and R₃ = 20 Ω. Find the unknown resistor R₄.

R₁ = 50 ΩR₂ = 40 ΩR₃ = 20 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 10 V, R₁ = 60 Ω and R₂ = 20 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 10 VR₁ = 60 ΩR₂ = 20 ΩR₃ = 300 ΩR₄ = 50 Ω

V_a = V

3.Medium

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 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 = 470 Ω

P_g = mW

4.Medium

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

V_s = 15 VR₁ = 120 ΩR₂ = 500 ΩR₃ = 120 ΩR₄ = 300 Ω

R_th = Ω

5.Hard

A strain gauge (GF = 2) on a member with E = 210 GPa forms a quarter bridge excited with 2.5 V. The output reads 0.5 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2V_o = 0.5 mVE = 210 GPa

σ = MPa

6.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 2.12 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.12ε = 1000 µε

V_o = mV

Answer key

1. R₄ = 16 Ω
2. V_a = 2.5 V
3. P_g = 13.3 mW
4. R_th = 182.5 Ω
5. σ = 84 MPa
6. V_o = 6.36 mV

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