Enjoyed the learning. Where were you forty years ago when I was sitting in the basement of a college listen to some old fart drone on about emf?
miles90 Alas, my purpose for responding was to address the idea that chargers limit or "cut" the power. They don't... as you verified with your Samsung charger. One wouldn't need a fuse resistor…
The power is determined by the inductive reactance of the primary coil. The reactance is given by the formula:
Xl = 2πfL f is the frequency of the AC current and L is the inductance of the primary coil…
Hi Karen, thank you for this very interesting video.
I have a little but very interesting problem for you. It took me a lot of time to find out but it's worth it.
Think about the small phone charger you use every day. These chargers are now very common and I use them to power digital chips that require 5 volts. These small devices are plugged directly to the main power line. These lines are (in France) protected with a 16A fuse. That means that these lines can deliver 15A at 230V or 15x230=3450 watts ! But these devices sometimes only deliver 0.75A at 5V or less then 5 watts.
The question is therefore, how do they cut all that power ?
Your problem is just one of the many implementations of step down transformers.
When you step down the voltage, you also step down the current. Power = Voltage * Current.
The design of these wall warts is a science all to itself.
You can see many different approaches to building an effect transformer solution.
Basically, you can play with power, voltage, current, efficiency, cost and safety.
Each design is a compromise of these factors.
Cheap wall warts are cheap for a reason.
They can be very dangerous.