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 the bridge shown, V_s = 2 V, R₁ = 800 Ω and R₂ = 800 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 2 VR₁ = 800 ΩR₂ = 800 ΩR₃ = 120 ΩR₄ = 50 Ω

V_a = V

2.Easy

In a slide-wire (metre) bridge a known 50 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 = 50 Ωl = 40 cmL = 100 cm

R_x = Ω

3.Medium

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (V_s = 2 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 2 VR₁ = 800 ΩR₂ = 150 ΩR₃ = 60 ΩR₄ = 250 ΩR_g = 20 Ω

I_g = µA

4.Medium

A bridge with four 470 Ω arms is supplied with 10 V. When the sensor R₂ changes, the output reads V_ab = 49.5 mV. Find the exact change ΔR of R₂.

V_s = 10 VR = 470 ΩV_ab = 49.5 mV

ΔR = Ω

5.Hard

A bridge with 350 Ω arms is excited with 2.5 V and has four active gauges, two in tension and two in compression (full bridge). The gauge factor is 2 and the strain is 1500 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 1500 µε

V_o = mV

6.Hard

A 120 Ω strain gauge with gauge factor 2.1 is bonded to a steel bar. Under load its resistance rises by 0.252 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.1ΔR = 0.252 Ω

ε = µε

Answer key

1. V_a = 1 V
2. R_x = 75 Ω
3. I_g = −6662 µA
4. ΔR = 9.399 Ω
5. V_o = 7.5 mV
6. ε = 1000 µε

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