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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 2 V.

V_s = 2 VR₁ = 40 ΩR₂ = 300 ΩR₃ = 400 ΩR₄ = 200 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 10 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 35 cm from the left end A of the 100 cm wire. Find R_x.

R = 10 Ωl = 35 cmL = 100 cm

R_x = Ω

3.Medium

A bridge with four 120 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 182.9 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 120 ΩV_ab = 182.9 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 = 9 VR₁ = 250 ΩR₂ = 500 ΩR₃ = 120 ΩR₄ = 40 Ω

R_th = Ω

5.Hard

A 120 Ω strain gauge with gauge factor 2.12 is bonded to a steel bar. Under load its resistance rises by 0.2544 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.12ΔR = 0.2544 Ω

ε = µε

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 2.5 V. Under load the output reads 0.625 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2V_o = 0.625 mV

ε = µε

Answer key

1. V_ab = 1.098 V
2. R_x = 18.57 Ω
3. ΔR = 6 Ω
4. R_th = 196.7 Ω
5. ε = 1000 µε
6. ε = 500 µε

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