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

In a slide-wire (metre) bridge a known 10 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 45 cm from the left end A of the 100 cm wire. Find R_x.

R = 10 Ωl = 45 cmL = 100 cm

R_x = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 800 Ω, R₂ = 1000 Ω and R₄ = 1000 Ω. Find the setting R₃.

R₁ = 800 ΩR₂ = 1000 ΩR₄ = 1000 Ω

R₃ = Ω

3.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 15 VR₁ = 50 ΩR₂ = 100 ΩR₃ = 300 ΩR₄ = 10 Ω

R_th = Ω

4.Medium

A bridge with four 220 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 74.26 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 220 ΩV_ab = 74.26 mV

ΔR = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2.1) is excited with 3 V. The largest strain to be measured is 1000 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 3 VGF = 2.1ε_max = 1000 µεV_FS = 5 V

G =

6.Hard

A 1000 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.525 Ω. Find the strain ε in microstrain (µε).

R = 1000 ΩGF = 2.1ΔR = 0.525 Ω

ε = µε

Answer key

1. R_x = 12.22 Ω
2. R₃ = 800 Ω
3. R_th = 43.01 Ω
4. ΔR = 4.4 Ω
5. G = 3175
6. ε = 250 µε

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