Consider the \$AC\$ circuit:

enter image description here

For various \$U\$ values set by the potentiometer, we have measured the current \$I\$ flowing through the circuit with and without core put inside the inductor \$L\$.

As a result we concluded that, without the core, the current was always bigger than with the core.

E.g.: for set \$U = 4V\$ the current with the core: \$I = 4.33 \; mA\$ and without the core \$ I = 26.9 \; mA\$.

The cylindrical-shaped core was made out of metal-alike material.


  • Given the fact that with the core the current was lower, what material could the core be made of? Ferromagnetic cores increase the current, right?
  • What exactly does the Atr in the schematic stands for?
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    \$\begingroup\$ Probably autotransformer. Is this homework? Are you aware of permeability? \$\endgroup\$ – winny Nov 16 '19 at 22:56
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    \$\begingroup\$ Not a homework, finished my physics lab and just curious afterwards. Reading about permeability right now, thanks. \$\endgroup\$ – weno Nov 16 '19 at 22:57
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    \$\begingroup\$ Good. Look up permeability and Al value. \$\endgroup\$ – winny Nov 16 '19 at 22:58
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    \$\begingroup\$ @weno I am split in feelings about your question. On the one hand, experiments like this are exactly the kind of thing about which you should NOT be told any answers. This is the kind of thing that can help you learn how to think about the world around you. There isn't really a right answer. In fact, it's possible that your own imagination might come up with something today that has never been published or discussed before and our world will be the better for it. Giving you the answer we have cuts short developing your imaginative powers. And that would be a sad loss. \$\endgroup\$ – jonk Nov 17 '19 at 6:13
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    \$\begingroup\$ @weno On the other, sometimes it's better to see the world standing on the shoulders of the giants who have come before you, too. So just telling you and letting you move on might be the better choice, too. Why do you think that a ferromagnetic core would increase the current? Can you explain your thinking about this? Why does it make sense? What's going on before adding the core and after, that makes you go this direction? Is it just something you read elsewhere and perhaps misinterpreted that is clouding your thinking now? \$\endgroup\$ – jonk Nov 17 '19 at 6:15

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