Elec Class
learn electricity hands-on
Solved exercise · level 5 of 5
Skills: Calculate
A coil 80 cm long with an inner cross-section of 8 cm² has 2000 turns; a second winding of 400 turns is wound over it. What current is needed in the first one to produce, by cutting it in 20 ms, an EMF of 22.9 mV across the 400 turns?
Parametric exercise: the values change with every draw; these are one example.
E = N₂ · B · S / Δt → B = E · Δt / (N₂ · S) = 0.00143 T; then B = 4π·10⁻⁷ · N₁ · I / l → I = B · l / (4π·10⁻⁷ · N₁) = 0.455 A.