Physics HW help! (current and circuits)

[FizzeL]

Ok I need help with the following problems. I already have the answers for all the problems. But I want to understand HOW to get the answers. I don't understand this and need help.


Answers:
E1 = 18v
E2 = 7v


Answers:
a) 20 ohms
b) A2: 4.00 A; A3: 12.0 A; A4: 14.0 A; A5: 8.00 A


Answers:
a) I = 2.0 A to left
b) R = 5 ohms
c) E = 42v

[Broccoli]

I'm in AP Physics this year, and I made a 100% on the test over circuits, but I have to leave in five minutes.

I might decide to help you if no one else has when I get a chance.

[Zetsumei]

I'll stick with my 1+1 = 2 kinda of stuff!

Sorry!

[Serjndestroy]

Still need help, Fizzel? As I think I will be able to help you with those...

[wyeth124]

Just finished num 59, but I need to scan it first as the method requires you to modified the diagramm a bit. As I´m currently no where near a scanner, will post my workings later.

[wyeth124]

Crap, somehow my scanner is not working. Alright, I´ll try to explain my workings as best as I can.

58 )Use both first and second Kirchhoff´s law for this problem. With the first law, find the current in the middle part of the circuit. I middle = 1A, flowing from right to left.

With this, you will already have all the equations needed. With the second law, find both E1 and E2 (with 2 loops).

60) To find I, use Kirchhoff´s first law. At the junction, 4A + I -6A = 0. Therefore, I = 2A, flowing to left.

Consider the bottom part, the total voltage is 3 Ohm x 6A = 18V. As the total voltage for parallel circuit are equal, compare the voltage from the bottom part with the top and middle parts.

18V = 28V - (2A)(R)
R = 5 Ohms

18V = E - (4A)(6 Ohm)
E = 42V

Note: The methods for num 58 & 60 are the same. Personally I would prefer to use the Kirchhoff´s laws, but finding and comparing the total volatges in parallel circuits will also work.

I will post my workings for num 59 if I can get my scanner to work.