Answer:
Please refer to the figure.
Explanation:
The crucial point here is to calculate the enclosed current. If the current I is flowing through the whole cross-sectional area of the wire, the current density is

The current density is constant for different parts of the wire. This idea is similar to that of the density of a glass of water is equal to the density of a whole bucket of water.
So,

This enclosed current is now to be used in Ampere’s Law.

Here,
represents the circular path of radius r. So we can replace the integral with the circumference of the path,
.
As a result, the magnetic field is

Answer:

Explanation:
Since <em>light is so fast</em> we can assume no time passes between the lightning strikes and we observe it. We want to know then how far away did the strike occur for the sound to take 16s to reach our ears. Since the definition of velocity tells us that
, we can write 
The ultimate energy source for wind comes from Earth's uneven heating on Earth's surface which can be caused mainly by the sun.
Answer: A, B, and D,
C is incorrect because continental drift takes several centuries to move the tectonic plates witch is not an immediate impact leaving you with A,B, and D.
Answer:
1750 Joules.
Explanation:
Work done = force * distance
= 7 * 250
= 1750 Joules.