Imagine diagram below is a rheostat
A _____________C____________ B
AB is the piece of wire while C is point of contact.
May I know what's essental in the construction of this
rheostat.
A. a constant cross sectional-area of wire from A to B
B. Type of wire used
C Length of AB
D None of the above
Intially I thought answer's C. But think again, if the cross
sectional area's not constant, then the length(where you move)
doesn't matter since resistance changes unevenly everything you
move! The area's affecting it all the time. Say you have a rheostat
that intially a large area, small area, large area, larger area,
then SMALLER area. In this case, current is always varying!
However, length matters but not as much because as long as you have
a piece of wire, if you say move it a little towards A, resistance
decreases, and current increases and vice versa for B. You can
control the current so long as you have a wire. (it all depends on
how well you move it to get your desired flow of current across)
Thus I think A is the answer.
What's your take? (:
