A permanent magnet picks up an iron nail, magnetizing the nail. How is this system different from an electromagnet?

Asteady current of 1 ais flowing through a conducter calculate the number of electrons that flows through conductor in 1second

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.

Does heating a metal wire increase or decrease its electrical resistance? why?