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 the bridge shown, V_s = 15 V, R₁ = 50 Ω and R₂ = 800 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 15 VR₁ = 50 ΩR₂ = 800 ΩR₃ = 120 ΩR₄ = 10 Ω

V_a = V

2.Easy

In a slide-wire (metre) bridge a known 50 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 80 cm from the left end A of the 100 cm wire. Find R_x.

R = 50 Ωl = 80 cmL = 100 cm

R_x = Ω

3.Medium

A bridge with four 1000 Ω arms is supplied with 6 V. When the sensor R₂ changes, the output reads V_ab = 14.93 mV. Find the exact change ΔR of R₂.

V_s = 6 VR = 1000 ΩV_ab = 14.93 mV

ΔR = Ω

4.Medium

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

V_s = 9 VR₁ = 150 ΩR₂ = 120 ΩR₃ = 10 ΩR₄ = 10 Ω

R_th = Ω

5.Hard

A strain gauge (GF = 2.1) on a member with E = 200 GPa forms a quarter bridge excited with 3 V. The output reads 0.63 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.1V_o = 0.63 mVE = 200 GPa

σ = MPa

6.Hard

A bridge with 350 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 2.1 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.1ε = 1500 µε

V_o = mV

Answer key

1. V_a = 14.12 V
2. R_x = 12.5 Ω
3. ΔR = 10 Ω
4. R_th = 71.67 Ω
5. σ = 80 MPa
6. V_o = 7.875 mV

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