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 = 500 Ω, R₂ = 120 Ω and R₃ = 200 Ω. Find the unknown resistor R₄.

R₁ = 500 ΩR₂ = 120 ΩR₃ = 200 Ω

R₄ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 800 Ω, R₂ = 20 Ω and R₄ = 120 Ω. Find the setting R₃.

R₁ = 800 ΩR₂ = 20 ΩR₄ = 120 Ω

R₃ = Ω

3.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 80 ΩR₂ = 250 ΩR₃ = 60 ΩR₄ = 800 ΩR_g = 50 Ω

I_g = µA

4.Medium

A bridge has four 250 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 1 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 9 VR = 250 ΩΔR = 1 Ω

V_ab = mV

5.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 1000 µε

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. R₄ = 48 Ω
2. R₃ = 4800 Ω
3. I_g = −12450 µA
4. V_ab = 9 mV
5. V_o = 1.5 mV
6. ε = 250 µε

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