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 = 15 V and its output is open. Find the current I_s drawn from the supply, in mA.

V_s = 15 VR₁ = 400 ΩR₂ = 80 ΩR₃ = 400 ΩR₄ = 1000 Ω

I_s = mA

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 20 Ω, R₂ = 400 Ω and R₃ = 60 Ω. Find the unknown resistor R₄.

R₁ = 20 ΩR₂ = 400 ΩR₃ = 60 Ω

R₄ = Ω

3.Medium

A bridge has four 100 Ω arms and V_s = 9 V. The sensor R₂ increases by ΔR = 8 Ω. Find the exact output V_ab in mV.

V_s = 9 VR = 100 ΩΔR = 8 Ω

V_ab = mV

4.Medium

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (V_s = 15 V). Find the galvanometer current I_g from a to b, in µA.

V_s = 15 VR₁ = 120 ΩR₂ = 60 ΩR₃ = 250 ΩR₄ = 200 ΩR_g = 50 Ω

I_g = µA

5.Hard

A load cell (a full bridge of strain gauges) has a rated output of 1 mV/V at its rated load of 50 kg. It is excited with 12 V. Find its output V_o under a load of 37.5 kg.

1 mV/VF_rated = 50 kgV_s = 12 VF = 37.5 kg

V_o = mV

6.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2 and the strain is 800 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2ε = 800 µε

V_o = mV

Answer key

1. I_s = 41.96 mA
2. R₄ = 1200 Ω
3. V_ab = 173.1 mV
4. I_g = −8287 µA
5. V_o = 9 mV
6. V_o = 1.2 mV

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