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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 6 V.

V_s = 6 VR₁ = 120 ΩR₂ = 60 ΩR₃ = 200 ΩR₄ = 40 Ω

V_ab = V

2.Easy

The bridge shown is supplied with V_s = 15 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 15 VR₁ = 800 ΩR₂ = 10 ΩR₃ = 600 ΩR₄ = 500 Ω

I_s = mA

3.Medium

A 350 Ω strain gauge is one arm (R₂) of a bridge with four equal 350 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 350 Ω

P_g = mW

4.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 = 100 ΩR₂ = 600 ΩR₃ = 300 ΩR₄ = 20 ΩR_g = 20 Ω

I_g = µA

5.Hard

A bridge with 120 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 2.12 and the strain is 500 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.12ε = 500 µε

V_o = mV

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 50 kg. It is excited with 12 V. Find its output V_o under a load of 12.5 kg.

2 mV/VF_rated = 50 kgV_s = 12 VF = 12.5 kg

V_o = mV

Answer key

1. V_ab = 1 V
2. I_s = 32.15 mA
3. P_g = 17.86 mW
4. I_g = 31923 µA
5. V_o = 3.18 mV
6. V_o = 6 mV

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