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 = 1000 Ω and R₃ = 500 Ω. Find the unknown resistor R₄.

R₁ = 250 ΩR₂ = 1000 ΩR₃ = 500 Ω

R₄ = Ω

2.Easy

In the bridge shown, V_s = 15 V, R₁ = 400 Ω and R₂ = 1000 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 15 VR₁ = 400 ΩR₂ = 1000 ΩR₃ = 120 ΩR₄ = 1000 Ω

V_a = V

3.Medium

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 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 = 470 Ω

P_g = mW

4.Medium

A 400 Ω strain gauge is one arm (R₂) of a bridge with four equal 400 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 = 400 Ω

P_g = mW

5.Hard

A quarter bridge (one active gauge, GF = 2.1) is excited with 10 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 = 10 VGF = 2.1ε_max = 1200 µεV_FS = 5 V

G =

6.Hard

A 350 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 1.103 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.1ΔR = 1.103 Ω

ε = µε

Answer key

1. R₄ = 2000 Ω
2. V_a = 10.71 V
3. P_g = 2.128 mW
4. P_g = 2.5 mW
5. G = 793.7
6. ε = 1500 µε

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