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 2 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 60 cm from the left end A of the 100 cm wire. Find R_x.

R = 2 Ωl = 60 cmL = 100 cm

R_x = Ω

2.Easy

The bridge shown is supplied with V_s = 9 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 9 VR₁ = 800 ΩR₂ = 10 ΩR₃ = 20 ΩR₄ = 250 Ω

I_s = mA

3.Medium

A bridge with four 1000 Ω arms is supplied with 9 V. When the sensor R₂ changes, the output reads V_ab = 254.7 mV. Find the exact change ΔR of R₂.

V_s = 9 VR = 1000 ΩV_ab = 254.7 mV

ΔR = Ω

4.Medium

A bridge has four 120 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 0.6 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 15 VR = 120 ΩΔR = 0.6 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 10 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 = 10 VGF = 2.05ε = 1000 µε

V_o = mV

6.Hard

A 120 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.2952 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.05ΔR = 0.2952 Ω

ε = µε

Answer key

1. R_x = 1.333 Ω
2. I_s = 44.44 mA
3. ΔR = 120 Ω
4. V_ab = 18.75 mV
5. V_o = 20.5 mV
6. ε = 1200 µε

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