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

R = 50 Ωl = 60 cmL = 100 cm

R_x = Ω

2.Easy

The bridge shown is supplied with V_s = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 250 ΩR₂ = 600 ΩR₃ = 800 ΩR₄ = 600 Ω

I_s = mA

3.Medium

A bridge with four 250 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 288.5 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 250 ΩV_ab = 288.5 mV

ΔR = Ω

4.Medium

A bridge has four 1000 Ω arms and V_s = 6 V. The sensor R₂ increases by ΔR = 2.5 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 6 VR = 1000 ΩΔR = 2.5 Ω

V_ab = mV

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output V_o under a load of 150 kg.

2.5 mV/VF_rated = 200 kgV_s = 10 VF = 150 kg

V_o = mV

6.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 1.281 mV. Find the axial stress σ in MPa.

V_s = 5 VGF = 2.05V_o = 1.281 mVE = 110 GPa

σ = MPa

Answer key

1. R_x = 33.33 Ω
2. I_s = 5.672 mA
3. ΔR = 20 Ω
4. V_ab = 3.75 mV
5. V_o = 18.75 mV
6. σ = 54.99 MPa

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