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 = 400 Ω, R₂ = 800 Ω and R₃ = 20 Ω. Find the unknown resistor R₄.

R₁ = 400 ΩR₂ = 800 ΩR₃ = 20 Ω

R₄ = Ω

2.Easy

In a slide-wire (metre) bridge a known 100 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 75 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 75 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 470 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 23.5 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 470 ΩΔR = 23.5 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 = 5 VR₁ = 100 ΩR₂ = 100 ΩR₃ = 300 ΩR₄ = 500 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 1000 kg. It is excited with 5 V. Find its output V_o under a load of 600 kg.

2 mV/VF_rated = 1000 kgV_s = 5 VF = 600 kg

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 3 V and has one active gauge (quarter 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 = 40 Ω
2. R_x = 33.33 Ω
3. V_ab = 24.39 mV
4. R_th = 237.5 Ω
5. V_o = 6 mV
6. V_o = 0.9 mV

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