Which is the best procedure to make a permanent magnet? a) placing a magnetically hard material in a weak magnetic field b) placing a magnetically hard material in a strong magnetic field c) placing a magnetically soft material in a weak magnetic field d) placing a magnetically soft material in a strong magnetic field

B) placing a magnetically hard material in a strong magnetic field

Explanation:

There are two type of magnetic materials in nature

1) Magnetic Hard materials

2) Magnetic soft materials

Here both materials are made up of domains which will not produce their own magnetic field due to their random arrangement

When we magnetize them by strong magnetic field then all domains will align themselves into the direction of magnetic field

Now if we use magnetic hard material then this alignment will last for long time but for magnetic soft material this alignment will change with time.

So in order to make strong permanent magnet the correct option would be

B) placing a magnetically hard material in a strong magnetic field

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.