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 = 150 Ω, R₂ = 300 Ω and R₃ = 400 Ω. Find the unknown resistor R₄.

R₁ = 150 ΩR₂ = 300 ΩR₃ = 400 Ω

R₄ = Ω

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 40 Ω, R₂ = 500 Ω and R₃ = 100 Ω. Find the unknown resistor R₄.

R₁ = 40 ΩR₂ = 500 ΩR₃ = 100 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 = 5 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 5 VR₁ = 20 ΩR₂ = 600 ΩR₃ = 10 ΩR₄ = 40 ΩR_g = 20 Ω

I_g = µA

4.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 9 VR₁ = 40 ΩR₂ = 400 ΩR₃ = 250 ΩR₄ = 120 Ω

R_th = Ω

5.Hard

A bridge with 350 Ω arms is excited with 5 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2ε = 1000 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output V_o under a load of 160 kg.

1 mV/VF_rated = 200 kgV_s = 10 VF = 160 kg

V_o = mV

Answer key

1. R₄ = 800 Ω
2. R₄ = 1250 Ω
3. I_g = 17711 µA
4. R_th = 117.4 Ω
5. V_o = 5 mV
6. V_o = 8 mV

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