12. A circuit with multiple resistors and a capacitor is s \"iown below. .\\, u u A. x, x, .\\ \\ u .\\I 51 82 . "" 250.0000 300.0000 12Vr 10.0uF At the start, both switches (81 and 82) are open as shown above and the capacitor is uncharged. a) S] is closed at t = Osec. How long does it take 'or the potential difference across the capacitor to hit 6.0V? b) The circuit is then le alone (with 51 closed) for a very long time. New 51 is opened simultaneously as S2. is closed. How long does it take (from the time 52 was closed) until the capacitor has 6.0V across it? 13. An American traveler in France carries a transformer to convert France= s standard 220 V to 120 V so that she can use some small appliances on her trip. (a) What is the ratio of turns in the primary and secondary coils of her transformer? (b) What is the ratio of input to output current? (c) Ifher hair dryer runs on 120 V and is rated at 2000 watts, what is her normal current? (d) What will be the needed input current to create the necessary output current? 15. For the circuit shown, use Kirchhoff's Laws to write a set of equations which are sufficient to solve for the unknown currents. R1=20 9 Ra=25 9 b AAAAA C AAAAA d 6.0 V 9.0 V 18 V R3=50 9 SAAAAA e h f -I1 +13 R4=40 Q a. Write Kirchoff's current law for junction f. b. Write Kirchoff's voltage rule for loop abcgfhia. C. Write Kirchoff's voltage rule for loop cdefgc d. Extra Credit: Solve the system to find the currents through the circuit