Energy of the magnetic field
Answers are for parents and teachers.
1
L = 0.6 H and I = 5 A. What is W in J?
7.5
2
I = 0.2 A and Φ = 50 mWb. What is W in mJ?
5
3
L = 0.3 H and W = 0.6 J. What is the current in A?
2
4
Why does the formula W = LI²/2 contain the factor ½?
The current grows from zero to I and Φ(I) is linear, so the average flux is Φ/2; the work equals the triangle's area.
5
Why is it dangerous to break the current in a coil with large inductance suddenly?
The fast change ΔI/Δt gives a large self-induced EMF (high voltage) and a spark.