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

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 500 Ω, R₂ = 800 Ω and R₃ = 20 Ω. Find the unknown resistor R₄.

R₁ = 500 ΩR₂ = 800 ΩR₃ = 20 Ω

R₄ = Ω

2.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 25 cm from the left end A of the 100 cm wire. Find R_x.

R = 50 Ωl = 25 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 50 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 = 20 ΩR₂ = 100 ΩR₃ = 60 ΩR₄ = 60 ΩR_g = 50 Ω

I_g = µA

4.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 6 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 6 VR₁ = 250 ΩR₂ = 100 ΩR₃ = 60 ΩR₄ = 40 ΩR_g = 200 Ω

I_g = µA

5.Hard

A quarter bridge with one active gauge (GF = 2.05) is excited with 10 V. Under load the output reads 1.025 mV. Find the strain ε in µε.

V_s = 10 VGF = 2.05V_o = 1.025 mV

ε = µε

6.Hard

A strain gauge (GF = 2.1) on a member with E = 210 GPa forms a quarter bridge excited with 3 V. The output reads 0.788 mV. Find the axial stress σ in MPa.

V_s = 3 VGF = 2.1V_o = 0.788 mVE = 210 GPa

σ = MPa

Answer key

1. R₄ = 32 Ω
2. R_x = 150 Ω
3. I_g = 31034 µA
4. I_g = −2321 µA
5. ε = 200 µε
6. σ = 105.1 MPa

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