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 = 3 V.

V_s = 3 VR₁ = 60 ΩR₂ = 120 ΩR₃ = 10 ΩR₄ = 60 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 100 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 70 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 70 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 2 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 2 VR₁ = 80 ΩR₂ = 80 ΩR₃ = 100 ΩR₄ = 50 ΩR_g = 200 Ω

I_g = µA

4.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 40 ΩR₂ = 50 ΩR₃ = 300 ΩR₄ = 60 ΩR_g = 50 Ω

I_g = µA

5.Hard

A strain gauge (GF = 2.05) on a member with E = 70 GPa forms a quarter bridge excited with 10 V. The output reads 7.688 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2.05V_o = 7.688 mVE = 70 GPa

σ = MPa

6.Hard

A bridge with 120 Ω arms is excited with 5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.12 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.12ε = 600 µε

V_o = mV

Answer key

1. V_ab = −0.5714 V
2. R_x = 42.86 Ω
3. I_g = 1220 µA
4. I_g = 9545 µA
5. σ = 105 MPa
6. V_o = 6.36 mV

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