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 = 800 Ω and R₂ = 20 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 800 ΩR₂ = 20 ΩR₃ = 500 ΩR₄ = 80 Ω

V_a = V

2.Easy

The bridge shown is supplied with V_s = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 100 ΩR₂ = 400 ΩR₃ = 250 ΩR₄ = 200 Ω

I_s = mA

3.Medium

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 400 Ω

P_g = mW

4.Medium

A bridge has four 330 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 0.825 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 2 VR = 330 ΩΔR = 0.825 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 1000 kg. It is excited with 5 V. Find its output V_o under a load of 200 kg.

2 mV/VF_rated = 1000 kgV_s = 5 VF = 200 kg

V_o = mV

6.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.175 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.175 Ω

ε = µε

Answer key

1. V_a = 0.04878 V
2. I_s = 25.33 mA
3. P_g = 5.625 mW
4. V_ab = 1.25 mV
5. V_o = 2 mV
6. ε = 250 µε

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