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 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 45 cm from the left end A of the 100 cm wire. Find R_x.

R = 100 Ωl = 45 cmL = 100 cm

R_x = Ω

2.Easy

The bridge shown is supplied with V_s = 12 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 12 VR₁ = 100 ΩR₂ = 250 ΩR₃ = 50 ΩR₄ = 400 Ω

I_s = mA

3.Medium

A bridge has four 150 Ω arms and V_s = 3 V. The sensor R₂ increases by ΔR = 37.5 Ω. Find the exact output V_ab in mV.

V_s = 3 VR = 150 ΩΔR = 37.5 Ω

V_ab = mV

4.Medium

A bridge has four 330 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 16.5 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 330 ΩΔR = 16.5 Ω

V_ab = mV

5.Hard

A quarter bridge (one active gauge, GF = 2.1) is excited with 5 V. The largest strain to be measured is 1200 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 5 VGF = 2.1ε_max = 1200 µεV_FS = 3.3 V

G =

6.Hard

A bridge with 1000 Ω arms is excited with 10 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 1200 µε. Find the bridge output V_o in mV.

V_s = 10 VGF = 2.12ε = 1200 µε

V_o = mV

Answer key

1. R_x = 122.2 Ω
2. I_s = 60.95 mA
3. V_ab = 166.7 mV
4. V_ab = 182.9 mV
5. G = 1048
6. V_o = 25.44 mV

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