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 = 10 V, R₁ = 200 Ω and R₂ = 10 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 10 VR₁ = 200 ΩR₂ = 10 ΩR₃ = 500 ΩR₄ = 1000 Ω

V_a = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 800 Ω, R₂ = 200 Ω and R₃ = 100 Ω. Find the unknown resistor R₄.

R₁ = 800 ΩR₂ = 200 ΩR₃ = 100 Ω

R₄ = Ω

3.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 120 ΩR₂ = 300 ΩR₃ = 120 ΩR₄ = 1000 ΩR_g = 50 Ω

I_g = µA

4.Medium

A bridge with four 150 Ω arms is supplied with 10 V. When the sensor R₂ changes, the output reads V_ab = 49.5 mV. Find the exact change ΔR of R₂.

V_s = 10 VR = 150 ΩV_ab = 49.5 mV

ΔR = Ω

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 1000 kg. It is excited with 12 V. Find its output V_o under a load of 400 kg.

2 mV/VF_rated = 1000 kgV_s = 12 VF = 400 kg

V_o = mV

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

V_s = 3 VGF = 2.05ε = 1000 µε

V_o = mV

Answer key

1. V_a = 0.4762 V
2. R₄ = 25 Ω
3. I_g = −8824 µA
4. ΔR = 3 Ω
5. V_o = 9.6 mV
6. V_o = 6.15 mV

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