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 = 40 Ω, R₂ = 20 Ω and R₃ = 120 Ω. Find the unknown resistor R₄.

R₁ = 40 ΩR₂ = 20 ΩR₃ = 120 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 5 V, R₁ = 10 Ω and R₂ = 120 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 5 VR₁ = 10 ΩR₂ = 120 ΩR₃ = 150 ΩR₄ = 200 Ω

V_a = V

3.Medium

A bridge with four 400 Ω arms is supplied with 6 V. When the sensor R₂ changes, the output reads V_ab = 115.4 mV. Find the exact change ΔR of R₂.

V_s = 6 VR = 400 ΩV_ab = 115.4 mV

ΔR = Ω

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 200 ΩR₂ = 150 ΩR₃ = 40 ΩR₄ = 10 ΩR_g = 500 Ω

I_g = µA

5.Hard

A bridge with 350 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 250 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 250 µε

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 3 V. Under load the output reads 0.75 mV. Find the strain ε in µε.

V_s = 3 VGF = 2V_o = 0.75 mV

ε = µε

Answer key

1. R₄ = 60 Ω
2. V_a = 4.615 V
3. ΔR = 32 Ω
4. I_g = 1155 µA
5. V_o = 0.375 mV
6. ε = 500 µε

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