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 = 6 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 6 VR₁ = 100 ΩR₂ = 150 ΩR₃ = 80 ΩR₄ = 120 Ω

I_s = mA

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

R = 100 Ωl = 25 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 = 5 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 5 VR₁ = 150 ΩR₂ = 800 ΩR₃ = 600 ΩR₄ = 100 ΩR_g = 20 Ω

I_g = µA

4.Medium

A bridge has four 300 Ω arms and V_s = 5 V. The sensor R₂ increases by ΔR = 60 Ω. Find the exact output V_ab in mV.

V_s = 5 VR = 300 ΩΔR = 60 Ω

V_ab = mV

5.Hard

A 120 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.369 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.05ΔR = 0.369 Ω

ε = µε

6.Hard

A bridge with 120 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2 and the strain is 500 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 500 µε

V_o = mV

Answer key

1. I_s = 54 mA
2. R_x = 300 Ω
3. I_g = 15068 µA
4. V_ab = 227.3 mV
5. ε = 1500 µε
6. V_o = 1.5 mV

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