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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 6 V.

V_s = 6 VR₁ = 60 ΩR₂ = 800 ΩR₃ = 50 ΩR₄ = 50 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 25 cm from the left end A of the 100 cm wire. Find R_x.

R = 5 Ωl = 25 cmL = 100 cm

R_x = Ω

3.Medium

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

V_s = 2 VR₁ = 300 ΩR₂ = 500 ΩR₃ = 80 ΩR₄ = 10 Ω

R_th = Ω

4.Medium

A bridge with four 1000 Ω arms is supplied with 10 V. When the sensor R₂ changes, the output reads V_ab = 24.88 mV. Find the exact change ΔR of R₂.

V_s = 10 VR = 1000 ΩV_ab = 24.88 mV

ΔR = Ω

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 100 kg. It is excited with 10 V. Find its output V_o under a load of 60 kg.

2.5 mV/VF_rated = 100 kgV_s = 10 VF = 60 kg

V_o = mV

6.Hard

A strain gauge (GF = 2.05) on a member with E = 200 GPa forms a quarter bridge excited with 5 V. The output reads 0.641 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.05V_o = 0.641 mVE = 200 GPa

σ = MPa

Answer key

1. V_ab = 2.581 V
2. R_x = 15 Ω
3. R_th = 196.4 Ω
4. ΔR = 10 Ω
5. V_o = 15 mV
6. σ = 50.03 MPa

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