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.

New worksheet Practise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________ Date: ____________

1.Easy

Find the open-circuit output voltage V_ab = V_a − V_b of the bridge shown, with V_s = 5 V.

V_s = 5 VR₁ = 60 ΩR₂ = 80 ΩR₃ = 120 ΩR₄ = 200 Ω

V_ab = V

2.Easy

The Wheatstone bridge in the diagram is balanced: the galvanometer reads zero. R₁ = 400 Ω, R₂ = 400 Ω and R₃ = 800 Ω. Find the unknown resistor R₄.

R₁ = 400 ΩR₂ = 400 ΩR₃ = 800 Ω

R₄ = Ω

3.Medium

A bridge has four 500 Ω arms and V_s = 2 V. The sensor R₂ increases by ΔR = 2 Ω. Using the small-change approximation, find the output V_ab in mV.

V_s = 2 VR = 500 ΩΔR = 2 Ω

V_ab = mV

4.Medium

A 250 Ω strain gauge is one arm (R₂) of a bridge with four equal 250 Ω arms and an excitation of 5 V. Find the power P_g dissipated in the gauge, in mW. Self-heating limits the excitation.

V_s = 5 VR = 250 Ω

P_g = mW

5.Hard

A 120 Ω strain gauge with gauge factor 2.05 is bonded to a steel bar. Under load its resistance rises by 0.1968 Ω. Find the strain ε in microstrain (µε).

R = 120 ΩGF = 2.05ΔR = 0.1968 Ω

ε = µε

6.Hard

A load cell (a full bridge of strain gauges) has a rated output of 3 mV/V at its rated load of 200 kg. It is excited with 5 V. Find its output V_o under a load of 150 kg.

3 mV/VF_rated = 200 kgV_s = 5 VF = 150 kg

V_o = mV

Answer key

1. V_ab = −0.2679 V
2. R₄ = 800 Ω
3. V_ab = 2 mV
4. P_g = 25 mW
5. ε = 800 µε
6. V_o = 11.25 mV

Full step-by-step solutions: practise this topic on examproblems.com.