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 = 10 V, R₁ = 400 Ω and R₂ = 250 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 10 VR₁ = 400 ΩR₂ = 250 ΩR₃ = 1000 ΩR₄ = 150 Ω

V_a = V

2.Easy

In a slide-wire (metre) bridge a known 50 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 = 50 Ωl = 60 cmL = 100 cm

R_x = Ω

3.Medium

A bridge has four 220 Ω arms and V_s = 15 V. The sensor R₂ increases by ΔR = 55 Ω. Find the exact output V_ab in mV.

V_s = 15 VR = 220 ΩΔR = 55 Ω

V_ab = mV

4.Medium

A bridge with four 330 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads V_ab = 9.9 mV. Find the exact change ΔR of R₂.

V_s = 2 VR = 330 ΩV_ab = 9.9 mV

ΔR = Ω

5.Hard

A bridge with 350 Ω arms is excited with 5 V and has one active gauge (quarter bridge). The gauge factor is 2.1 and the strain is 750 µε. Find the bridge output V_o in mV.

V_s = 5 VGF = 2.1ε = 750 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 3 V. The largest strain to be measured is 1000 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 3 VGF = 2ε_max = 1000 µεV_FS = 3.3 V

G =

Answer key

1. V_a = 3.846 V
2. R_x = 33.33 Ω
3. V_ab = 833.3 mV
4. ΔR = 6.599 Ω
5. V_o = 1.969 mV
6. G = 2200

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