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 = 10 V.

V_s = 10 VR₁ = 120 ΩR₂ = 20 ΩR₃ = 50 ΩR₄ = 1000 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 40 cm from the left end A of the 100 cm wire. Find R_x.

R = 5 Ωl = 40 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 = 3 VR₁ = 300 ΩR₂ = 20 ΩR₃ = 800 ΩR₄ = 200 Ω

R_th = Ω

4.Medium

A bridge with four 350 Ω arms is supplied with 5 V. When the sensor R₂ changes, the output reads V_ab = 12.44 mV. Find the exact change ΔR of R₂.

V_s = 5 VR = 350 ΩV_ab = 12.44 mV

ΔR = Ω

5.Hard

A bridge with 350 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 750 µε

V_o = mV

6.Hard

A bridge with 120 Ω arms is excited with 2.5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 200 µε

V_o = mV

Answer key

1. V_ab = −8.095 V
2. R_x = 7.5 Ω
3. R_th = 178.8 Ω
4. ΔR = 3.501 Ω
5. V_o = 7.688 mV
6. V_o = 1 mV

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