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 = 600 ΩR₃ = 100 ΩR₄ = 300 Ω

I_s = mA

2.Easy

The bridge shown is supplied with V_s = 15 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 15 VR₁ = 20 ΩR₂ = 50 ΩR₃ = 300 ΩR₄ = 600 Ω

I_s = mA

3.Medium

A 250 Ω strain gauge is one arm (R₂) of a bridge with four equal 250 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 = 250 Ω

P_g = mW

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 15 VR₁ = 150 ΩR₂ = 600 ΩR₃ = 60 ΩR₄ = 800 Ω

R_th = Ω

5.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.84 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.84 Ω

ε = µε

6.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 5 V. The largest strain to be measured is 400 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 5 VGF = 2.05ε_max = 400 µεV_FS = 2.5 V

G =

Answer key

1. I_s = 38.57 mA
2. I_s = 231 mA
3. P_g = 25 mW
4. R_th = 175.8 Ω
5. ε = 1200 µε
6. G = 2439

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