Why does the number of coils, the current and the ype of core affect the strength of the electromagnet

Explanation:

The magnetic field due to the current carrying coil is given by

Where, n be the number of turns, I be the current and is the absolute permeability.

Here, we observe that the strength of electromagnet is proportional to n,  I and .

So, as the number of turns increases or the current increases, the strength of electromagnet increases.

If the core is filled with any other material then relative permeability is also added. So, the nature of core also affects the strength of electromagnet.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.