PHY 122 Exam 100 Points Total Name 3. (14 pts.) A 100m long metal wire has a cro

Question

PHY 122 Exam 100 Points Total Name 3. (14 pts.) A 100m long metal wire has a cross-sectional area of 10-6 m2. The potential difference between the two ends of the wire is 1.5 V. A current of 50 A is running through the wire. (a) (3 pts.) What is the rate of energy loss of the wire? (b) (3 pts.) What is the resistance of the wire? (c) (4 pts.) What is the resistivity of the metal that the wire is made of? (d) (3 pts.) If you increase the temperature of the wire, do you expect the current to increase or decrease? Briefly few sentences at most explain your answer. (If you wish, you may draw a picture to go with your explanation. A picture is optional, not compulsory).

Explanation / Answer

1) power lost=V*I=75 W

2)resistance=1.5/50=0.03 A

3)resistivity=R*area/length=3*10(-10)

4) if temp rises,the R will increase so I will decrease as with increasing temp,kinetic energy of molecules increase and they obstruct the path of free electrons increasing resistance so current decreases

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