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 a slide-wire (metre) bridge a known 2 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 = 2 Ωl = 60 cmL = 100 cm

R_x = Ω

2.Easy

In the bridge shown, V_s = 9 V, R₁ = 100 Ω and R₂ = 50 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 9 VR₁ = 100 ΩR₂ = 50 ΩR₃ = 1000 ΩR₄ = 300 Ω

V_a = V

3.Medium

A 350 Ω strain gauge is one arm (R₂) of a bridge with four equal 350 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 = 350 Ω

P_g = mW

4.Medium

A bridge has four 400 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 80 Ω. Find the exact output V_ab in mV.

V_s = 2 VR = 400 ΩΔR = 80 Ω

V_ab = mV

5.Hard

A bridge with 1000 Ω arms is excited with 2.5 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 400 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.05ε = 400 µε

V_o = mV

6.Hard

A quarter bridge with one active gauge (GF = 2.12) is excited with 3 V. Under load the output reads 1.272 mV. Find the strain ε in µε.

V_s = 3 VGF = 2.12V_o = 1.272 mV

ε = µε

Answer key

1. R_x = 1.333 Ω
2. V_a = 3 V
3. P_g = 2.857 mW
4. V_ab = 90.91 mV
5. V_o = 0.5125 mV
6. ε = 800 µε

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