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 = 12 V, R₁ = 300 Ω and R₂ = 10 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 12 VR₁ = 300 ΩR₂ = 10 ΩR₃ = 80 ΩR₄ = 100 Ω

V_a = V

2.Easy

The Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 50 Ω, R₂ = 80 Ω and R₄ = 40 Ω. Find the setting R₃.

R₁ = 50 ΩR₂ = 80 ΩR₄ = 40 Ω

R₃ = Ω

3.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 200 ΩR₂ = 120 ΩR₃ = 120 ΩR₄ = 1000 ΩR_g = 50 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 = 15 VR₁ = 1000 ΩR₂ = 120 ΩR₃ = 1000 ΩR₄ = 500 Ω

R_th = Ω

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 5 V. Find its output V_o under a load of 75 kg.

1.5 mV/VF_rated = 100 kgV_s = 5 VF = 75 kg

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2.05) is excited with 10 V. The largest strain to be measured is 400 µε, and it must give 2.5 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 10 VGF = 2.05ε_max = 400 µεV_FS = 2.5 V

G =

Answer key

1. V_a = 0.3871 V
2. R₃ = 25 Ω
3. I_g = −33462 µA
4. R_th = 440.5 Ω
5. V_o = 5.625 mV
6. G = 1220

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