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 = 6 V, R₁ = 80 Ω and R₂ = 1000 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 6 VR₁ = 80 ΩR₂ = 1000 ΩR₃ = 600 ΩR₄ = 600 Ω

V_a = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 60 Ω and R₃ = 20 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 60 ΩR₃ = 20 Ω

R₄ = Ω

3.Medium

A bridge has four 300 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 75 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 300 ΩΔR = 75 Ω

V_ab = mV

4.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 10 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 10 VR = 500 Ω

P_g = mW

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output V_o under a load of 150 kg.

1.5 mV/VF_rated = 200 kgV_s = 10 VF = 150 kg

V_o = mV

6.Hard

A 350 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.3587 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.05ΔR = 0.3587 Ω

ε = µε

Answer key

1. V_a = 5.556 V
2. R₄ = 60 Ω
3. V_ab = 111.1 mV
4. P_g = 50 mW
5. V_o = 11.25 mV
6. ε = 500 µε

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