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 the bridge shown, V_s = 2 V, R₁ = 300 Ω and R₂ = 800 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 300 ΩR₂ = 800 ΩR₃ = 60 ΩR₄ = 50 Ω

V_a = V

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 5 V.

V_s = 5 VR₁ = 100 ΩR₂ = 300 ΩR₃ = 200 ΩR₄ = 800 Ω

V_ab = V

3.Medium

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

V_s = 9 VR₁ = 120 ΩR₂ = 200 ΩR₃ = 40 ΩR₄ = 40 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 10 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 10 VR₁ = 50 ΩR₂ = 20 ΩR₃ = 150 ΩR₄ = 80 ΩR_g = 200 Ω

I_g = µA

5.Hard

A 120 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.123 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.05ΔR = 0.123 Ω

ε = µε

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 100 kg. It is excited with 10 V. Find its output V_o under a load of 25 kg.

1.5 mV/VF_rated = 100 kgV_s = 10 VF = 25 kg

V_o = mV

Answer key

1. V_a = 1.455 V
2. V_ab = −0.25 V
3. R_th = 95 Ω
4. I_g = −2331 µA
5. ε = 500 µε
6. V_o = 3.75 mV

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