Can anyone help me on this dc circuits, again?

Question

here's the link:

http://allizione.multiply.com/photos/album/3/physics_help_again_dc_circuits

please. especially the third figure. but if you can figure out also how the resistors in ALL figures are connected, it will be of much help. thanks

Answer 1

All the three circuits are in parallel.

Req of the first circuit in parallel is 12/13 ohms.

Req of the second circuit in parallel is 12/13 ohms.

Req of third circuit in parallel is 12/25 ohms.

3 ohms and 4 ohms resistors are in parallel.

Answer 2

In Figures 1 and 2, all the resistor are connected in parallel.

The point is, it doesn't matter what shape or how long the connecting liens are -- they are considered to have Zero 0hms. [The only time this has any real effect is in highspeed switching circuits, like computers]

In Figure 3, the points D and E could be considered the "common" (sometimes called "ground" but "common" is more correct) point of the circuit.  Again, in this case it doesn't matter what shape or how long the connecting lines are -- the 3-ohm and 4-ohm resistors are in parallel with each other.

Without my calculator, my best guess is that the voltage appearing at Point B (with D or E as common) is between 15 and 17 volts.