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 Wheatstone bridge in the diagram is balanced by adjusting R₃. R₁ = 200 Ω, R₂ = 20 Ω and R₄ = 300 Ω. Find the setting R₃.

R₁ = 200 ΩR₂ = 20 ΩR₄ = 300 Ω

R₃ = Ω

2.Easy

In a slide-wire (metre) bridge a known 100 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 60 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 60 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 500 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 75 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 500 ΩΔR = 75 Ω

V_ab = mV

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 = 250 ΩR₂ = 200 ΩR₃ = 250 ΩR₄ = 120 ΩR_g = 500 Ω

I_g = µA

5.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 250 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2ε_max = 250 µεV_FS = 3.3 V

G =

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 50 kg. It is excited with 5 V. Find its output V_o under a load of 40 kg.

3 mV/VF_rated = 50 kgV_s = 5 VF = 40 kg

V_o = mV

Answer key

1. R₃ = 3000 Ω
2. R_x = 66.67 Ω
3. V_ab = 523.3 mV
4. I_g = 520.6 µA
5. G = 10560
6. V_o = 12 mV

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