When a direct current is connected to the two ends of an electrical coil, a magnetic field is generated. Why?

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If a constant current source is connected in time between the two terminals of the coil, the starting electric current generates a magnetic field according to the Biot – Savart Act. You are here: https://en.wikipedia.org/wiki/Roll_and_And_Record_Word And here: https://en.wikipedia.org/wiki/Biot%E2% 80% 93Savart-t% C3% B6rv% C3% A9ny 
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