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 = 300 ΩR₃ = 50 ΩR₄ = 200 Ω

I_s = mA

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 10 V.

V_s = 10 VR₁ = 600 ΩR₂ = 10 ΩR₃ = 400 ΩR₄ = 100 Ω

V_ab = V

3.Medium

A galvanometer with a resistance of 500 Ω is connected between a and b of the bridge shown (V_s = 10 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 10 VR₁ = 50 ΩR₂ = 120 ΩR₃ = 10 ΩR₄ = 800 ΩR_g = 500 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 = 60 ΩR₂ = 10 ΩR₃ = 1000 ΩR₄ = 400 Ω

R_th = Ω

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 100 kg. It is excited with 5 V. Find its output V_o under a load of 60 kg.

2.5 mV/VF_rated = 100 kgV_s = 5 VF = 60 kg

V_o = mV

6.Hard

A bridge with 350 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2ε = 750 µε

V_o = mV

Answer key

1. I_s = 44.18 mA
2. V_ab = −1.836 V
3. I_g = −5169 µA
4. R_th = 294.3 Ω
5. V_o = 7.5 mV
6. V_o = 3.75 mV

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