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 = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 40 ΩR₂ = 500 ΩR₃ = 120 ΩR₄ = 150 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 250 Ω, R₂ = 600 Ω and R₃ = 120 Ω. Find the unknown resistor R₄.

R₁ = 250 ΩR₂ = 600 ΩR₃ = 120 Ω

R₄ = Ω

3.Medium

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

V_s = 6 VR₁ = 500 ΩR₂ = 1000 ΩR₃ = 400 ΩR₄ = 50 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 9 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 9 VR₁ = 200 ΩR₂ = 400 ΩR₃ = 10 ΩR₄ = 50 ΩR_g = 50 Ω

I_g = µA

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1.5 mV/V at its rated load of 100 kg. It is excited with 10 V. Find its output V_o under a load of 40 kg.

1.5 mV/VF_rated = 100 kgV_s = 10 VF = 40 kg

V_o = mV

6.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 750 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.1ε = 750 µε

V_o = mV

Answer key

1. I_s = 33.33 mA
2. R₄ = 288 Ω
3. R_th = 377.8 Ω
4. I_g = −7826 µA
5. V_o = 6 mV
6. V_o = 4.725 mV

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