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 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 75 cm from the left end A of the 100 cm wire. Find R_x.

R = 50 Ωl = 75 cmL = 100 cm

R_x = Ω

2.Easy

In a slide-wire (metre) bridge a known 10 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 75 cm from the left end A of the 100 cm wire. Find R_x.

R = 10 Ωl = 75 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 330 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 16.5 Ω. Find the exact output V_ab in mV.

V_s = 3 VR = 330 ΩΔR = 16.5 Ω

V_ab = mV

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 500 ΩR₂ = 60 ΩR₃ = 600 ΩR₄ = 200 ΩR_g = 500 Ω

I_g = µA

5.Hard

A strain gauge (GF = 2) on a member with E = 200 GPa forms a quarter bridge excited with 10 V. The output reads 3.75 mV. Find the axial stress σ in MPa.

V_s = 10 VGF = 2V_o = 3.75 mVE = 200 GPa

σ = MPa

6.Hard

A 120 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.1008 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.1ΔR = 0.1008 Ω

ε = µε

Answer key

1. R_x = 16.67 Ω
2. R_x = 3.333 Ω
3. V_ab = 36.59 mV
4. I_g = −2437 µA
5. σ = 150 MPa
6. ε = 400 µε

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