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 = 800 Ω, R₂ = 200 Ω and R₃ = 800 Ω. Find the unknown resistor R₄.

R₁ = 800 ΩR₂ = 200 ΩR₃ = 800 Ω

R₄ = Ω

2.Easy

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 70 cm from the left end A of the 100 cm wire. Find R_x.

R = 20 Ωl = 70 cmL = 100 cm

R_x = Ω

3.Medium

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

V_s = 10 VR₁ = 300 ΩR₂ = 200 ΩR₃ = 120 ΩR₄ = 500 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 = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 600 ΩR₂ = 1000 ΩR₃ = 80 ΩR₄ = 20 ΩR_g = 500 Ω

I_g = µA

5.Hard

A quarter bridge with one active gauge (GF = 2.05) is excited with 3 V. Under load the output reads 0.384 mV. Find the strain ε in µε.

V_s = 3 VGF = 2.05V_o = 0.384 mV

ε = µε

6.Hard

A bridge with 350 Ω arms is excited with 10 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.12 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.12ε = 200 µε

V_o = mV

Answer key

1. R₄ = 200 Ω
2. R_x = 8.571 Ω
3. R_th = 216.8 Ω
4. I_g = 5724 µA
5. ε = 249.8 µε
6. V_o = 4.24 mV

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