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 = 500 Ω, R₂ = 20 Ω and R₄ = 20 Ω. Find the setting R₃.

R₁ = 500 ΩR₂ = 20 ΩR₄ = 20 Ω

R₃ = Ω

2.Easy

In a slide-wire (metre) bridge a known 10 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 = 10 Ωl = 60 cmL = 100 cm

R_x = Ω

3.Medium

Find the Thévenin resistance R_th of the bridge shown, seen from the output terminals a and b.

V_s = 12 VR₁ = 300 ΩR₂ = 200 ΩR₃ = 200 ΩR₄ = 50 Ω

R_th = Ω

4.Medium

A galvanometer with a resistance of 200 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 = 1000 ΩR₂ = 100 ΩR₃ = 150 ΩR₄ = 1000 ΩR_g = 200 Ω

I_g = µA

5.Hard

A bridge with 350 Ω arms is excited with 2.5 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 200 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2ε = 200 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2.1) is excited with 2.5 V. The largest strain to be measured is 200 µε, and it must give 3.3 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 2.5 VGF = 2.1ε_max = 200 µεV_FS = 3.3 V

G =

Answer key

1. R₃ = 500 Ω
2. R_x = 6.667 Ω
3. R_th = 160 Ω
4. I_g = −9240 µA
5. V_o = 0.5 mV
6. G = 12571

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