You want to use a metal bar as a resistor.Its dimensions are 2 by 4 by 10 units.To get the smallest resistance from this bar,you should attach leads to the two opposite sides that have the dimensions of
A)2 by 4 units.
B)2 by 10 units.
C)4 by 10 units.
D)any number of units because all connections give the same resistance.
E)None of these is correct.

Question

Quizplus · Accepted Answer

The resistance of a metal bar is given by R = ρL/A, where ρ is the resistivity of the metal, L is the length of the bar, and A is its cross-sectional area. The resistance is smallest when the cross-sectional area is largest. In this case, the dimensions of the bar are 2 by 4 by 10, so the cross-sectional area of the sides with dimensions 4 by 10 is 40 square units. This is larger than the cross-sectional areas of the other sides, so attaching leads to the 4 by 10 sides will give the smallest resistance.

You Want to Use a Metal Bar as a Resistor