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 bridge shown is supplied with V_s = 5 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 5 VR₁ = 120 ΩR₂ = 40 ΩR₃ = 500 ΩR₄ = 400 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 120 Ω, R₂ = 120 Ω and R₃ = 200 Ω. Find the unknown resistor R₄.

R₁ = 120 ΩR₂ = 120 ΩR₃ = 200 Ω

R₄ = Ω

3.Medium

A bridge has four 150 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 30 Ω. Find the exact output V_ab in mV.

V_s = 5 VR = 150 ΩΔR = 30 Ω

V_ab = mV

4.Medium

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

V_s = 2 VR₁ = 80 ΩR₂ = 300 ΩR₃ = 400 ΩR₄ = 800 Ω

R_th = 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 50 kg. It is excited with 12 V. Find its output V_o under a load of 30 kg.

2 mV/VF_rated = 50 kgV_s = 12 VF = 30 kg

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 2.5 V. Under load the output reads 0.938 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2V_o = 0.938 mV

ε = µε

Answer key

1. I_s = 36.81 mA
2. R₄ = 200 Ω
3. V_ab = 227.3 mV
4. R_th = 329.8 Ω
5. V_o = 14.4 mV
6. ε = 750.4 µε

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