## PHYS345 Electricity and Electronics

**Answers for 9/2 Assignment**

**Answer for 2.9**
0.89 mA

**Answer for 2.11**

a. 2.53 kW

b. 60.7 kW-hr

c. $3.64

**Answer for 2.13**

The terminal voltage is 7 V.

The delivered power is 7 mW.

The efficiency is 58%.

**Answer for 2.38**

- Assuming a load resistance of 5 ohm,
- I find the source resistance to be 0.1 ohm.
- If the load resistance is increased to 10 ohm, the terminal voltage will rise to 25.25 V.
- If the voltage source can endure it, the short circuit current will be 255 A.

- Alternatively, assuming a load resistance of 5 W at 25 V dictates a load resistance of 125 ohm,
- Then the source resistance must be 2.5 ohm.
- If the load resistance is decreased to 10 ohm, the terminal voltage will drop to 20.4 V.
- The short circuit current will be 10.2 A.

**Answer for 2.40**
300 m of AWG 8 has a resistance of about 0.6 ohm.

**Answer for 2.54**

a) The initial internal resistance is about 0.06 ohm.

b) One year later the internal resistance has risen to 84 ohm.

"http://www.physics.udel.edu/~watson/phys345/protected/exercises/answers/0902.html"

Last updated Sept. 9, 1999.

Copyright George Watson, Univ. of Delaware, 1999.