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

The bridge shown is supplied with V_s = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 800 ΩR₂ = 20 ΩR₃ = 50 ΩR₄ = 40 Ω

I_s = mA

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

R = 100 Ωl = 55 cmL = 100 cm

R_x = Ω

3.Medium

A 330 Ω strain gauge is one arm (R₂) of a bridge with four equal 330 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 330 Ω

P_g = mW

4.Medium

A bridge has four 470 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 1.88 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 5 VR = 470 ΩΔR = 1.88 Ω

V_ab = mV

5.Hard

A bridge with 350 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.12 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.12ε = 1000 µε

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2.05) is excited with 3 V. Under load the output reads 1.845 mV. Find the strain ε in µε.

V_s = 3 VGF = 2.05V_o = 1.845 mV

ε = µε

Answer key

1. I_s = 148 mA
2. R_x = 81.82 Ω
3. P_g = 3.03 mW
4. V_ab = 5 mV
5. V_o = 10.6 mV
6. ε = 1200 µε

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