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: the galvanometer reads zero. R₁ = 600 Ω, R₂ = 80 Ω and R₃ = 600 Ω. Find the unknown resistor R₄.

R₁ = 600 ΩR₂ = 80 ΩR₃ = 600 Ω

R₄ = 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 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

3.Medium

A 100 Ω strain gauge is one arm (R₂) of a bridge with four equal 100 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 = 100 Ω

P_g = mW

4.Medium

A 470 Ω strain gauge is one arm (R₂) of a bridge with four equal 470 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 = 470 Ω

P_g = mW

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 200 kg. It is excited with 5 V. Find its output V_o under a load of 160 kg.

2 mV/VF_rated = 200 kgV_s = 5 VF = 160 kg

V_o = mV

6.Hard

A 1000 Ω strain gauge with gauge factor 2 is bonded to a steel bar. Under load its resistance rises by 1.6 Ω. Find the strain ε in microstrain (µε).

R = 1000 ΩGF = 2ΔR = 1.6 Ω

ε = µε

Answer key

1. R₄ = 80 Ω
2. R_x = 122.2 Ω
3. P_g = 62.5 mW
4. P_g = 4.787 mW
5. V_o = 8 mV
6. ε = 800 µε

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