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 = 120 ΩR₂ = 250 ΩR₃ = 250 ΩR₄ = 80 Ω

V_ab = V

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 30 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 30 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 100 Ω arms and V_s = 10 V. The sensor R₂ increases by ΔR = 25 Ω. Find the exact output V_ab in mV.

V_s = 10 VR = 100 ΩΔR = 25 Ω

V_ab = mV

4.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

5.Hard

A 350 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.7175 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.05ΔR = 0.7175 Ω

ε = µε

6.Hard

A bridge with 120 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 750 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 750 µε

V_o = mV

Answer key

1. V_ab = 0.8665 V
2. R_x = 233.3 Ω
3. V_ab = 555.6 mV
4. P_g = 62.5 mW
5. ε = 1000 µε
6. V_o = 0.9609 mV

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