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

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 12 V.

V_s = 12 VR₁ = 10 ΩR₂ = 100 ΩR₃ = 80 ΩR₄ = 50 Ω

V_ab = V

2.Easy

In a slide-wire (metre) bridge a known 20 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 55 cm from the left end A of the 100 cm wire. Find R_x.

R = 20 Ωl = 55 cmL = 100 cm

R_x = Ω

3.Medium

A 500 Ω strain gauge is one arm (R₂) of a bridge with four equal 500 Ω arms and an excitation of 2 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 2 VR = 500 Ω

P_g = mW

4.Medium

A 1000 Ω strain gauge is one arm (R₂) of a bridge with four equal 1000 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 1000 Ω

P_g = mW

5.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 10 V. The largest strain to be measured is 250 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 = 2ε_max = 250 µεV_FS = 2.5 V

G =

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2.5 mV/V at its rated load of 200 kg. It is excited with 10 V. Find its output V_o under a load of 40 kg.

2.5 mV/VF_rated = 200 kgV_s = 10 VF = 40 kg

V_o = mV

Answer key

1. V_ab = 6.294 V
2. R_x = 16.36 Ω
3. P_g = 2 mW
4. P_g = 6.25 mW
5. G = 2000
6. V_o = 5 mV

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