What do we call a collection of matter that does not interact with anything else in the universe?
A. The forces that act in a collision
B. An intergalactic highway
C. An isolated system
D. A system in which collisions always occur

Currents in dc transmission lines can be 100 a or higher. some people are concerned that the electromagnetic fields from such lines near their homes could pose health dangers. for a line that has current 150 a and a height of 8.0 m above the ground, what magnetic field does the line produce at ground level? express your answer in teslas and as a percentage of the earth’s magnetic field, which is 0.50 g. is this value cause for worry?