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

In the bridge shown, V_s = 5 V, R₁ = 600 Ω and R₂ = 400 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 5 VR₁ = 600 ΩR₂ = 400 ΩR₃ = 80 ΩR₄ = 250 Ω

V_a = V

2.Easy

The bridge shown is supplied with V_s = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 150 ΩR₂ = 600 ΩR₃ = 20 ΩR₄ = 200 Ω

I_s = mA

3.Medium

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

V_s = 6 VR₁ = 50 ΩR₂ = 1000 ΩR₃ = 40 ΩR₄ = 40 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 500 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 = 600 ΩR₃ = 40 ΩR₄ = 10 ΩR_g = 500 Ω

I_g = µA

5.Hard

A bridge with 350 Ω arms is excited with 3 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2.1 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.1ε = 800 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 37.5 kg.

2.5 mV/VF_rated = 50 kgV_s = 10 VF = 37.5 kg

V_o = mV

Answer key

1. V_a = 2 V
2. I_s = 35.27 mA
3. R_th = 67.62 Ω
4. I_g = 594.6 µA
5. V_o = 5.04 mV
6. V_o = 18.75 mV

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