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: the galvanometer reads zero. R₁ = 250 Ω, R₂ = 200 Ω and R₃ = 120 Ω. Find the unknown resistor R₄.

R₁ = 250 ΩR₂ = 200 ΩR₃ = 120 Ω

R₄ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 150 Ω, R₂ = 400 Ω and R₄ = 300 Ω. Find the setting R₃.

R₁ = 150 ΩR₂ = 400 ΩR₄ = 300 Ω

R₃ = Ω

3.Medium

A 150 Ω strain gauge is one arm (R₂) of a bridge with four equal 150 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 150 Ω

P_g = mW

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 2 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 2 VR₁ = 10 ΩR₂ = 1000 ΩR₃ = 80 ΩR₄ = 250 ΩR_g = 500 Ω

I_g = µA

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 100 kg. It is excited with 10 V. Find its output V_o under a load of 50 kg.

1.5 mV/VF_rated = 100 kgV_s = 10 VF = 50 kg

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 5 V. Under load the output reads 1.25 mV. Find the strain ε in µε.

V_s = 5 VGF = 2V_o = 1.25 mV

ε = µε

Answer key

1. R₄ = 96 Ω
2. R₃ = 112.5 Ω
3. P_g = 6.667 mW
4. I_g = 815.1 µA
5. V_o = 7.5 mV
6. ε = 500 µε

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