Induktion und die Wirbelströme

Dose geht, (genauso wie alles, wo ein Magnet dran hält), Tasse nicht. 
Wie klein die Dose sein darf, hängt vom Modell ab.

Siehe hier:


https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.st.com/resource/en/application_note/cd00115561.pdf&ved=2ahUKEwil3qbE46nfAhVDFCwKHXCKDjQQFjAWegQIBxAB&usg=AOvVaw1mbkzlgGDlu2ZVOgLaG9HF

MfG

"No pot is on the plate, so the voltage drop is not big enough to exceed 
the pot detection threshold (PDT), set by software at 500 mV. The PWM 
signal is stopped, and the powering sequence is repeated after a break 
of 10 seconds.
Powering the plate continuously in order to detect a pot would result in 
an increase in power consumption. However, no parts would burn or be 
damaged. The break of 10 seconds between one powering sequence and 
another reduces power consumption while keeping full functionality and 
pot control."