Question

plz do question number 16

Answer 1

a)
1.North pole of magnet is towards loop and it is approaching to loop so no of magnetic field lines 
are increasing so polarity of loop will be north (N) for opposing increment in magnetic field lines
2. As loop's polarity is north so filed lines due to it reaching in solenoid will be increasing so 
for same opposing purpose polarity of solenoid also will be N 

b) An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of a large number of closely spaced turns of wire that create the magnetic field. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet. 
while permanent magnets are never loss its magnetism . these are some special type of material 

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