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

R = 100 Ωl = 25 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 = 800 ΩR₂ = 80 ΩR₃ = 1000 ΩR₄ = 10 Ω

I_s = mA

3.Medium

A galvanometer with a resistance of 500 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 = 150 ΩR₂ = 10 ΩR₃ = 400 ΩR₄ = 300 ΩR_g = 500 Ω

I_g = µA

4.Medium

A bridge with four 120 Ω arms is supplied with 15 V. When the sensor R₂ changes, the output reads V_ab = 37.31 mV. Find the exact change ΔR of R₂.

V_s = 15 VR = 120 ΩV_ab = 37.31 mV

ΔR = Ω

5.Hard

A bridge with 1000 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2ε = 800 µε

V_o = mV

6.Hard

A strain gauge (GF = 2) on a member with E = 200 GPa forms a quarter bridge excited with 2.5 V. The output reads 1.25 mV. Find the axial stress σ in MPa.

V_s = 2.5 VGF = 2V_o = 1.25 mVE = 200 GPa

σ = MPa

Answer key

1. R_x = 300 Ω
2. I_s = 6.379 mA
3. I_g = −1075 µA
4. ΔR = 1.2 Ω
5. V_o = 8 mV
6. σ = 200 MPa

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