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 = 1000 Ω, R₂ = 800 Ω and R₄ = 40 Ω. Find the setting R₃.

R₁ = 1000 ΩR₂ = 800 ΩR₄ = 40 Ω

R₃ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 80 Ω, R₂ = 400 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 80 ΩR₂ = 400 ΩR₃ = 600 Ω

R₄ = Ω

3.Medium

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (V_s = 6 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 6 VR₁ = 10 ΩR₂ = 1000 ΩR₃ = 20 ΩR₄ = 60 ΩR_g = 20 Ω

I_g = µA

4.Medium

A 200 Ω strain gauge is one arm (R₂) of a bridge with four equal 200 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 = 200 Ω

P_g = mW

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 1000 kg. It is excited with 12 V. Find its output V_o under a load of 400 kg.

1 mV/VF_rated = 1000 kgV_s = 12 VF = 400 kg

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.05ε = 600 µε

V_o = mV

Answer key

1. R₃ = 50 Ω
2. R₄ = 3000 Ω
3. I_g = 32084 µA
4. P_g = 11.25 mW
5. V_o = 4.8 mV
6. V_o = 1.537 mV

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