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 by adjusting R₃. R₁ = 800 Ω, R₂ = 300 Ω and R₄ = 600 Ω. Find the setting R₃.

R₁ = 800 ΩR₂ = 300 ΩR₄ = 600 Ω

R₃ = Ω

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

R = 5 Ωl = 25 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 200 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 10 ΩR₂ = 50 ΩR₃ = 40 ΩR₄ = 120 ΩR_g = 200 Ω

I_g = µA

4.Medium

A 330 Ω strain gauge is one arm (R₂) of a bridge with four equal 330 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 = 330 Ω

P_g = mW

5.Hard

A quarter bridge with one active gauge (GF = 2) is excited with 10 V. Under load the output reads 3 mV. Find the strain ε in µε.

V_s = 10 VGF = 2V_o = 3 mV

ε = µε

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 2 mV/V at its rated load of 50 kg. It is excited with 10 V. Find its output V_o under a load of 40 kg.

2 mV/VF_rated = 50 kgV_s = 10 VF = 40 kg

V_o = mV

Answer key

1. R₃ = 1600 Ω
2. R_x = 15 Ω
3. I_g = 5245 µA
4. P_g = 18.94 mW
5. ε = 600 µε
6. V_o = 16 mV

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