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 = 20 Ω, R₂ = 500 Ω and R₃ = 20 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 500 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 45 cm from the left end A of the 100 cm wire. Find R_x.

R = 50 Ωl = 45 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 10 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 10 VR₁ = 20 ΩR₂ = 120 ΩR₃ = 80 ΩR₄ = 20 ΩR_g = 200 Ω

I_g = µA

4.Medium

A galvanometer with a resistance of 100 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 = 50 ΩR₂ = 400 ΩR₃ = 250 ΩR₄ = 200 ΩR_g = 100 Ω

I_g = µA

5.Hard

A quarter bridge with one active gauge (GF = 2.05) is excited with 5 V. Under load the output reads 1.025 mV. Find the strain ε in µε.

V_s = 5 VGF = 2.05V_o = 1.025 mV

ε = µε

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 1200 µε, and it must give 5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2ε_max = 1200 µεV_FS = 5 V

G =

Answer key

1. R₄ = 500 Ω
2. R_x = 61.11 Ω
3. I_g = 28186 µA
4. I_g = 20870 µA
5. ε = 400 µε
6. G = 3333

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