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 = 250 Ω, R₂ = 250 Ω and R₃ = 800 Ω. Find the unknown resistor R₄.

R₁ = 250 ΩR₂ = 250 ΩR₃ = 800 Ω

R₄ = Ω

2.Easy

The bridge shown is supplied with V_s = 3 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 3 VR₁ = 80 ΩR₂ = 300 ΩR₃ = 80 ΩR₄ = 150 Ω

I_s = mA

3.Medium

A 1000 Ω strain gauge is one arm (R₂) of a bridge with four equal 1000 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 1000 Ω

P_g = mW

4.Medium

A galvanometer with a resistance of 100 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 = 600 ΩR₂ = 250 ΩR₃ = 800 ΩR₄ = 50 ΩR_g = 100 Ω

I_g = µA

5.Hard

A 120 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.36 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2ΔR = 0.36 Ω

ε = µε

6.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.525 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.525 Ω

ε = µε

Answer key

1. R₄ = 800 Ω
2. I_s = 20.94 mA
3. P_g = 1 mW
4. I_g = 2182 µA
5. ε = 1500 µε
6. ε = 750 µε

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