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 Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 100 Ω, R₂ = 150 Ω and R₄ = 300 Ω. Find the setting R₃.

R₁ = 100 ΩR₂ = 150 ΩR₄ = 300 Ω

R₃ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 80 Ω, R₂ = 40 Ω and R₄ = 250 Ω. Find the setting R₃.

R₁ = 80 ΩR₂ = 40 ΩR₄ = 250 Ω

R₃ = Ω

3.Medium

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

P_g = mW

4.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 40 ΩR₂ = 250 ΩR₃ = 500 ΩR₄ = 120 ΩR_g = 200 Ω

I_g = µA

5.Hard

A bridge with 1000 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 500 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 500 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 100 kg. It is excited with 12 V. Find its output V_o under a load of 40 kg.

3 mV/VF_rated = 100 kgV_s = 12 VF = 40 kg

V_o = mV

Answer key

1. R₃ = 200 Ω
2. R₃ = 500 Ω
3. P_g = 9 mW
4. I_g = 30272 µA
5. V_o = 1.5 mV
6. V_o = 14.4 mV

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