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 a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 80 cm from the left end A of the 100 cm wire. Find R_x.

R = 5 Ωl = 80 cmL = 100 cm

R_x = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 80 Ω, R₂ = 60 Ω and R₄ = 300 Ω. Find the setting R₃.

R₁ = 80 ΩR₂ = 60 ΩR₄ = 300 Ω

R₃ = Ω

3.Medium

A bridge with four 500 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads V_ab = 36.59 mV. Find the exact change ΔR of R₂.

V_s = 3 VR = 500 ΩV_ab = 36.59 mV

ΔR = Ω

4.Medium

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

V_s = 10 VR₁ = 200 ΩR₂ = 60 ΩR₃ = 800 ΩR₄ = 120 Ω

R_th = Ω

5.Hard

A bridge with 1000 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 1500 µε

V_o = mV

6.Hard

A 120 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.18 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2ΔR = 0.18 Ω

ε = µε

Answer key

1. R_x = 1.25 Ω
2. R₃ = 400 Ω
3. ΔR = 25 Ω
4. R_th = 150.5 Ω
5. V_o = 1.922 mV
6. ε = 750 µε

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