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

In the bridge shown, V_s = 6 V, R₁ = 300 Ω and R₂ = 120 Ω. Find the voltage V_a of node a with respect to the negative supply rail.

V_s = 6 VR₁ = 300 ΩR₂ = 120 ΩR₃ = 500 ΩR₄ = 250 Ω

V_a = V

2.Easy

In a slide-wire (metre) bridge a known 50 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 80 cm from the left end A of the 100 cm wire. Find R_x.

R = 50 Ωl = 80 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 = 10 VR₁ = 100 ΩR₂ = 600 ΩR₃ = 200 ΩR₄ = 50 Ω

R_th = Ω

4.Medium

A bridge with four 100 Ω arms is supplied with 2 V. When the sensor R₂ changes, the output reads V_ab = 24.39 mV. Find the exact change ΔR of R₂.

V_s = 2 VR = 100 ΩV_ab = 24.39 mV

ΔR = Ω

5.Hard

A quarter bridge (one active gauge, GF = 2) is excited with 2.5 V. The largest strain to be measured is 400 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 = 2ε_max = 400 µεV_FS = 3.3 V

G =

6.Hard

A bridge with 1000 Ω arms is excited with 3 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 200 µε. Find the bridge output V_o in mV.

V_s = 3 VGF = 2.05ε = 200 µε

V_o = mV

Answer key

1. V_a = 1.714 V
2. R_x = 12.5 Ω
3. R_th = 125.7 Ω
4. ΔR = 5 Ω
5. G = 6600
6. V_o = 0.3075 mV

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