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 = 20 Ω and R₂ = 60 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 15 VR₁ = 20 ΩR₂ = 60 ΩR₃ = 500 ΩR₄ = 400 Ω

V_a = V

2.Easy

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 30 cm from the left end A of the 100 cm wire. Find R_x.

R = 20 Ωl = 30 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (V_s = 9 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 9 VR₁ = 400 ΩR₂ = 40 ΩR₃ = 250 ΩR₄ = 100 ΩR_g = 100 Ω

I_g = µA

4.Medium

A bridge with four 300 Ω arms is supplied with 12 V. When the sensor R₂ changes, the output reads V_ab = 339.6 mV. Find the exact change ΔR of R₂.

V_s = 12 VR = 300 ΩV_ab = 339.6 mV

ΔR = Ω

5.Hard

A strain gauge (GF = 2.05) on a member with E = 110 GPa forms a quarter bridge excited with 5 V. The output reads 1.537 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.05V_o = 1.537 mVE = 110 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 750 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.1ε = 750 µε

V_o = mV

Answer key

1. V_a = 11.25 V
2. R_x = 46.67 Ω
3. I_g = −8437 µA
4. ΔR = 36 Ω
5. σ = 65.98 MPa
6. V_o = 3.938 mV

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