## PHYS345 Electricity and Electronics

**Answer for P3.2**
Source substitution leads to the following circuit:

The current through 900 ohm experiencing 7.0 V is 7.78 mA;
thus the current through *R*_{2} must be 2.78 mA.
Accordingly its resistance must be 1800 ohm.

**Answer for E3.6**

(*R*_{hot} - *R*_{cold})/*R*_{cold} = 4.5
for the stated temperature coefficient and temperature increase.
Thus the current surge must be 5.5 times the orerating current for this situation.

**Answer for E3.12**

*I*_{1} = 0.75 A

*I*_{2} = 0.25 A

*V*_{x} = 2.5 V

"http://www.physics.udel.edu/~watson/phys345/protected/exercises/answers/P3-2.html"

Last updated Sept. 23, 1998.

Copyright George Watson, Univ. of Delaware, 1998.