| Difficulty | Secondary School | High school/other |
| ★ | Basic | Easy |
| ★★ | Demanding | Basic |
| ★★★ | Demanding | |
| ★★★★ | Difficult | |
| ★★★★★ | Very difficult |
Determine the inductance of the coil and the phase between the voltage and the electric current.
Tip: ${U{_{R{_L}}}}^2+{U{_L}}^2= {U{_{R{_L}+L}}}^2$
Answer: $0{,}71\ mH$ ; $1{,}1°$