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 = 10 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 10 VR₁ = 200 ΩR₂ = 500 ΩR₃ = 150 ΩR₄ = 200 Ω

I_s = mA

2.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 15 V.

V_s = 15 VR₁ = 20 ΩR₂ = 500 ΩR₃ = 10 ΩR₄ = 50 Ω

V_ab = V

3.Medium

A galvanometer with a resistance of 500 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 = 60 ΩR₂ = 20 ΩR₃ = 400 ΩR₄ = 300 ΩR_g = 500 Ω

I_g = µA

4.Medium

A galvanometer with a resistance of 20 Ω is connected between a and b of the bridge shown (V_s = 12 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 12 VR₁ = 20 ΩR₂ = 40 ΩR₃ = 1000 ΩR₄ = 120 ΩR_g = 20 Ω

I_g = µA

5.Hard

A bridge with 120 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 2.1 and the strain is 1000 µε. Find the bridge output V_o in mV.

V_s = 2.5 VGF = 2.1ε = 1000 µε

V_o = mV

6.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 10 V. The largest strain to be measured is 1000 µε, and it must give 10 V at the input of an analogue-to-digital converter. Find the amplifier gain G.

V_s = 10 VGF = 2ε_max = 1000 µεV_FS = 10 V

G =

Answer key

1. I_s = 42.86 mA
2. V_ab = 1.923 V
3. I_g = −1301 µA
4. I_g = 47797 µA
5. V_o = 5.25 mV
6. G = 2000

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