The magnetic field created by an infinitely long wire carrying a current, which is given by Equation (28.9), will be used extensively. Of course, there is no such thing as an infinitely long wire! The field of a finite length of wire is derived -- Equation (28.8) -- and the infinite wire field is the result of taking the limit as the length of the wire becomes infinite. How long is "long enough" to be considered infinite? It's easy to say "when the length of the wire is much larger than the distance from it", but that doesn't give an intuitive feel for realistic dimensions. Consider a mechanical analogy: I can approximate the Earth as flat in the immediate region where I'm standing, because the radius of curvature of the Earth is very large compared to my dimensions. I can do the same on the Moon, but not on a basketball. However, bacteria or other single-cell organisms could probably approximate the basketball as flat at their location.

carbon is found in all living things. carbon atoms move constantly through

living organisms, the oceans, the atmosphere, and the earth’s crust in what is

known as the carbon cycle. the directions taken by carbon atoms through this

cycle are very complicated and can take millions of years to make a full circle.

all animals, from humans to the dinosaurs are part of the carbon cycle. when

animals eat food, they get carbon in the form of carbohydrates and proteins.

in animals, oxygen combines with food in the cells to produce energy for daily

activity and then gives off carbon. the carbon combines with oxygen to form

carbon dioxide (co2) and is released back into the atmosphere as a waste

product when animals breathe and exhale.

from 145-65 million years ago, earth was much

hotter than today and covered with dense,

tropical swamp forests. the trees and other

plants were immense and

provided an endless supply of

food for the giant animals that

roamed the land. somewhere in

the air above one of these

forests, a lone carbon atom has joined

up with two oxygen atoms to form a molecule of co2.

the co2 molecule was sucked into the tiny holes (stomata) on the leaf of a

fern plant and joined with sunlight, chlorophyll and water to make food and

energy in the plant’s cells through photosynthesis. the oxygen (o2) from the

co2 molecule was sent back into the atmosphere; the carbon atom (c) was

detached and used to make a molecule of sugar.

if that carbon atom had been eaten instead, a totally

different situation would have developed. let’s say

that a giant plant-eating dinosaur (herbivore) ate the

fern for breakfast, and swallowed the carbon in the

fern in the form of carbohydrates and proteins. in

the process of respiration, oxygen combined with

the carbohydrates and proteins in the dinosaur’s cells

to provide energy for its daily activity.  

a=d/t

a="triangle"v/t

explanation:

a = acceleration

the only real purpose of sputnik 1 was to beat the us into space. we were getting close to launching a useful satellite, explorer 1 - which launched on january 31, 1958. the ussr had to beat that, so they launched sputnik 1 on october 4, 19