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 bridge shown is supplied with V_s = 9 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 9 VR₁ = 20 ΩR₂ = 400 ΩR₃ = 600 ΩR₄ = 120 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 1000 Ω, R₂ = 500 Ω and R₄ = 250 Ω. Find the setting R₃.

R₁ = 1000 ΩR₂ = 500 ΩR₄ = 250 Ω

R₃ = Ω

3.Medium

A bridge with four 470 Ω arms is supplied with 3 V. When the sensor R₂ changes, the output reads V_ab = 84.91 mV. Find the exact change ΔR of R₂.

V_s = 3 VR = 470 ΩV_ab = 84.91 mV

ΔR = Ω

4.Medium

A galvanometer with a resistance of 100 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 = 20 ΩR₂ = 40 ΩR₃ = 150 ΩR₄ = 100 ΩR_g = 100 Ω

I_g = µA

5.Hard

A 1000 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 3.15 Ω. Find the strain ε in microstrain (µε).

R = 1000 ΩGF = 2.1ΔR = 3.15 Ω

ε = µε

6.Hard

A bridge with 1000 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 750 µε

V_o = mV

Answer key

1. I_s = 33.93 mA
2. R₃ = 500 Ω
3. ΔR = 56.4 Ω
4. I_g = 23077 µA
5. ε = 1500 µε
6. V_o = 0.9609 mV

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