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 = 60 Ω, R₂ = 120 Ω and R₃ = 250 Ω. Find the unknown resistor R₄.

R₁ = 60 ΩR₂ = 120 ΩR₃ = 250 Ω

R₄ = Ω

2.Easy

In a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 55 cm from the left end A of the 100 cm wire. Find R_x.

R = 5 Ωl = 55 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 100 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 100 ΩR₂ = 10 ΩR₃ = 400 ΩR₄ = 10 ΩR_g = 100 Ω

I_g = µA

4.Medium

A bridge with four 250 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 = 250 ΩV_ab = 37.31 mV

ΔR = Ω

5.Hard

A quarter bridge with one active gauge (GF = 2.1) is excited with 2.5 V. Under load the output reads 0.656 mV. Find the strain ε in µε.

V_s = 2.5 VGF = 2.1V_o = 0.656 mV

ε = µε

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 1000 kg. It is excited with 12 V. Find its output V_o under a load of 250 kg.

2 mV/VF_rated = 1000 kgV_s = 12 VF = 250 kg

V_o = mV

Answer key

1. R₄ = 500 Ω
2. R_x = 4.091 Ω
3. I_g = 8396 µA
4. ΔR = 2.5 Ω
5. ε = 499.8 µε
6. V_o = 6 mV

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