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 = 60 Ω and R₃ = 120 Ω. Find the unknown resistor R₄.

R₁ = 50 ΩR₂ = 60 ΩR₃ = 120 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 12 V, R₁ = 40 Ω and R₂ = 10 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 40 ΩR₂ = 10 ΩR₃ = 80 ΩR₄ = 400 Ω

V_a = V

3.Medium

A bridge has four 1000 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 4 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 10 VR = 1000 ΩΔR = 4 Ω

V_ab = mV

4.Medium

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

P_g = mW

5.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2.12 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.12ε = 1500 µε

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 600 µε

V_o = mV

Answer key

1. R₄ = 144 Ω
2. V_a = 2.4 V
3. V_ab = 10 mV
4. P_g = 4.787 mW
5. V_o = 2.385 mV
6. V_o = 1.8 mV

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