Kate gathered three boxes of the same size made of different materials: glass, clear plastic, and aluminum painted black. she placed them on a window sill i0n the sun for an hour and then measured the warmth of the air in each box. in this experiment, the types of box materials are a(n)

a. independent variable.

b. constant

c. control

d. dependent variable

20) what is a magnetic field? 21) in which direction do magnetic field lines always point? 22) sketch a diagram showing how a plotting compass points around a 23) name two magnetic poles that will: a) attract each other b) repel each other. 24) explain why you can use a compass to navigate. 25) what's an electromagnet? 26) list two ways to increase the strength of an electromagnet. 27) the wire in a simple motor feels a force when a current flows through it. why is this? i need answers to check mine