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 Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 40 Ω, R₂ = 1000 Ω and R₄ = 150 Ω. Find the setting R₃.

R₁ = 40 ΩR₂ = 1000 ΩR₄ = 150 Ω

R₃ = Ω

3.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 5 VR₁ = 60 ΩR₂ = 200 ΩR₃ = 120 ΩR₄ = 300 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 1000 ΩR₂ = 800 ΩR₃ = 600 ΩR₄ = 60 ΩR_g = 500 Ω

I_g = µA

5.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 5 V. Under load the output reads 1.06 mV. Find the strain ε in µε.

V_s = 5 VGF = 2.12V_o = 1.06 mV

ε = µε

6.Hard

A bridge with 1000 Ω arms is excited with 5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 750 µε

V_o = mV

Answer key

1. R_x = 300 Ω
2. R₃ = 6 Ω
3. R_th = 131.9 Ω
4. I_g = 1062 µA
5. ε = 400 µε
6. V_o = 7.5 mV

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