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 bridge shown is supplied with V_s = 2 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 2 VR₁ = 800 ΩR₂ = 60 ΩR₃ = 40 ΩR₄ = 600 Ω

I_s = mA

2.Easy

In a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 40 cm from the left end A of the 100 cm wire. Find R_x.

R = 5 Ωl = 40 cmL = 100 cm

R_x = Ω

3.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 15 VR₁ = 60 ΩR₂ = 500 ΩR₃ = 200 ΩR₄ = 500 Ω

R_th = Ω

4.Medium

A 200 Ω strain gauge is one arm (R₂) of a bridge with four equal 200 Ω arms and an excitation of 3 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 3 VR = 200 Ω

P_g = mW

5.Hard

A 350 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 0.84 Ω. Find the strain ε in microstrain (µε).

R = 350 ΩGF = 2ΔR = 0.84 Ω

ε = µε

6.Hard

A 120 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.063 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.1ΔR = 0.063 Ω

ε = µε

Answer key

1. I_s = 5.451 mA
2. R_x = 7.5 Ω
3. R_th = 196.4 Ω
4. P_g = 11.25 mW
5. ε = 1200 µε
6. ε = 250 µε

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