الفيزياء العامة الجزء الثاني#موقع الفيزياء.كوم

Lectures in General Physics
7.8 Solution of some selected problems
Example 7.9
Two wires A and B of circular cross section are made of the same metal
and have equal length, but the resistance of wire A is three times
greater than that of wire B. What is the ratio of their cross-sectional
area? How do their radii compare?
Solution
Since R=ρL/A, the ratio of the resistance R A /R B =A A /A B . Hence, the ratio is
three times. That is, the area of wire B is three times that of B.
The radius of wire b is √3 times the radius of wire B.
Example 7.10
Two conductors of the same length and radius are connected across the
same potential difference. One conductor has twice the resistance of
the other. Which conductor will dissipate more power?
Solution
Since the power dissipated is given by P=V 2 /R, the conductor with the lower
resistance will dissipate more power.
Dr. Hazem Falah Sakeek