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
5 ΩRₓBGACD40 cm

In a slide-wire (metre) bridge a known 5 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 40 cm from the left end A of the 100 cm wire. Find Rx.

R = 5 Ωl = 40 cmL = 100 cm
Rx = Ω
2.Easy
100 ΩRₓBGACD65 cm

In a slide-wire (metre) bridge a known 100 Ω resistor sits in the left gap and an unknown resistor Rₓ in the right gap. The galvanometer reads zero when the jockey is 65 cm from the left end A of the 100 cm wire. Find Rx.

R = 100 Ωl = 65 cmL = 100 cm
Rx = Ω
3.Medium
+−2 VR1​ = 100 ΩR2​ = 150 ΩR3​ = 150 ΩR4​ = 20 ΩabGRg​ = 50 Ω

A galvanometer with a resistance of 50 Ω is connected between a and b of the bridge shown (Vs = 2 V). Find the galvanometer current Ig from a to b, in µA.

Vs = 2 VR1 = 100 ΩR2 = 150 ΩR3 = 150 ΩR4 = 20 ΩRg = 50 Ω
Ig = µA
4.Medium
+−12 VR1​ = 120 ΩR2​ = 120 ΩR3​ = 60 ΩR4​ = 100 ΩabGRg​ = 20 Ω

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

Vs = 12 VR1 = 120 ΩR2 = 120 ΩR3 = 60 ΩR4 = 100 ΩRg = 20 Ω
Ig = µA
5.Hard
+−3 V1000 Ω − ΔR1000 Ω + ΔR1000 Ω1000 Ωab+−Vo​ = ?

A bridge with 1000 Ω arms is excited with 3 V and has two active gauges in adjacent arms, one in tension and one in compression (half bridge). The gauge factor is 2.12 and the strain is 250 µε. Find the bridge output Vo in mV.

Vs = 3 VGF = 2.12ε = 250 µε
Vo = mV
6.Hard
+−10 V350 Ω350 Ω + ΔR350 Ω350 Ωab+−Vo​ = ?

A bridge with 350 Ω arms is excited with 10 V and has one active gauge (quarter bridge). The gauge factor is 2.05 and the strain is 400 µε. Find the bridge output Vo in mV.

Vs = 10 VGF = 2.05ε = 400 µε
Vo = mV

Answer key

  1. 1. Rx = 7.5 Ω
  2. 2. Rx = 53.85 Ω
  3. 3. Ig = 7558 µA
  4. 4. Ig = −12766 µA
  5. 5. Vo = 0.795 mV
  6. 6. Vo = 2.05 mV

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