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 bridge shown is supplied with V_s = 9 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 9 VR₁ = 800 ΩR₂ = 120 ΩR₃ = 500 ΩR₄ = 120 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 200 Ω, R₂ = 1000 Ω and R₃ = 250 Ω. Find the unknown resistor R₄.

R₁ = 200 ΩR₂ = 1000 ΩR₃ = 250 Ω

R₄ = Ω

3.Medium

A galvanometer with a resistance of 20 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 = 10 ΩR₂ = 1000 ΩR₃ = 500 ΩR₄ = 10 ΩR_g = 20 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 = 3 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 3 VR₁ = 1000 ΩR₂ = 400 ΩR₃ = 50 ΩR₄ = 50 ΩR_g = 100 Ω

I_g = µA

5.Hard

A 350 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.861 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2.05ΔR = 0.861 Ω

ε = µε

6.Hard

A bridge with 120 Ω arms is excited with 10 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.05 and the strain is 600 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.05ε = 600 µε

V_o = mV

Answer key

1. I_s = 24.3 mA
2. R₄ = 1250 Ω
3. I_g = 73328 µA
4. I_g = −1565 µA
5. ε = 1200 µε
6. V_o = 6.15 mV

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