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 = 3 V.

V_s = 3 VR₁ = 120 ΩR₂ = 100 ΩR₃ = 800 ΩR₄ = 40 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 50 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 = 50 Ωl = 60 cmL = 100 cm

R_x = Ω

3.Medium

A 100 Ω strain gauge is one arm (R₂) of a bridge with four equal 100 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 100 Ω

P_g = mW

4.Medium

A bridge has four 470 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 1.88 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 10 VR = 470 ΩΔR = 1.88 Ω

V_ab = mV

5.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 1000 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 0.06 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2ΔR = 0.06 Ω

ε = µε

Answer key

1. V_ab = 1.221 V
2. R_x = 33.33 Ω
3. P_g = 62.5 mW
4. V_ab = 10 mV
5. V_o = 1.5 mV
6. ε = 250 µε

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