Electric Circuit Help: Finding Current and Voltage in a Complex Circuit

In summary, the conversation involves a question about finding the current and voltage in a given electric circuit. The participants discuss using Kirchoff's laws and adding resistors in series or parallel to solve the problem. A diagram is provided and eventually a solution is obtained using Kirchoff's laws. The concept of negative currents is also explained.
  • #1
Winner
94
8
Electric Circuit help!

Ok here's my question:

For the cirucit shown in the drawing(attached), find the current (I) through the 2.00 ohm resistor and the voltage (V) of the battery to the left of this resistor.

Ok, should I be using Kirchoff's drop=rise, and junction rules?

It doesn't seem to work because my voltage is also unknown. Could I possibly add them resistors in series/parallel?

Any directions appreciated. Thanks :confused:
 

Attachments

  • Ohms.JPG
    Ohms.JPG
    4.7 KB · Views: 537
Physics news on Phys.org
  • #2
Your attachment is not downloadable. You need to resubmit.
Note the following msg above your attachment:
"Attachments Pending Approval"


~~
 
  • #3
Hmm, I can download it without problems. Well here it is again.
 

Attachments

  • Ohms.JPG
    Ohms.JPG
    4.7 KB · Views: 442
  • #4
Ok for those who can't get it:


4ohm 8ohm
|---/\/\/\-----/\/\/\---|
| ---->3amps |
|__/\/\/\_______|l____|
| 6ohm 24V |
| <--- I=? |
|___|l________/\/\/\__|
V=? 2ohm

That's the best I can do with keyboard lol.
 
  • #5
Darn, picture got messed up. sorry. The I=? is suppose to be far right, so with the 24 V.
 
  • #6
Winner said:
Ok for those who can't get it:


4ohm 8ohm
|---/\/\/\-----/\/\/\---|
| ---->3amps |
|__/\/\/\_______|l____|
| 6ohm 24V |
| <--- I=? |
|___|l________/\/\/\__|
V=? 2ohm

That's the best I can do with keyboard lol.
Which branch (top or middle) does the "3 amps" refer to??
(Hint: Enclose such diagrams within CODE & /CODE tags to preserve spacing.)

~~
 
  • #7
It refers to the top one, and the one you have to find refers to the bottom one, sorry. I'm not too familiar with tags but I'll keep that in mind thanks.
 
  • #8
Code:
     4ohm       8ohm
|---/\/\/\-----/\/\/\---|
|     3amps ---->       |
|                       |
|__/\/\/\_______|l______|
|   6ohm        24V     |
|                       |
|            <---- [COLOR=Red]I=?[/COLOR]  |
|___|l________/\/\/\____|
    [COLOR=Red]V=?[/COLOR]        2ohm
The solution is obtained using Kirchoff's Laws. For this purpose, the following are established:
{(+) Current Direction in Top Branch} = {Left-to-Right} = IT
{(+) Current Direction in Middle Branch} = {Right-to-Left} = IM
{(+) Current Direction in Bottom Branch} = {Right-to-Left} = IB

We first note the Top Branch has equiv resistance RT=(4 + 8)=(12 Ω) thru which flows (3 amps), thereby indicating a voltage drop (using Ohm's Law) of ΔV=(-)(3 amps)*(12 ohms)=(-36 V). Thus, applying Kirchoff's Laws:
(1) ---> Voltage Loop Clockwise Top & Middle Branches
Begin top-left corner (clockwise):
(-36 V) + (24 V) - (6 ohms)*IM = 0
::: ⇒ IM = (-2 amps)

(2) ---> Current Node Left Side Middle Branch
Into node is (+):
IM + IB - IT = 0
::: ⇒ (-2 amps) + IB - (3 amps) = 0
::: ⇒ IB = (5 amps)

(3) ---> Voltage Loop Clockwise Top & Bottom Branches
Begin top-left corner (clockwise):
(-36 V) - (2 ohms)*IB + VB = 0
::: ⇒ (-36 V) - (2 ohms)*(5 amps) + VB = 0
::: ⇒ VB = (46 V)



~~
 
Last edited:
  • #9
IM = (-2 amps)

what does negative currents mean? flow the opposite direction?
 
  • #10
F|234K said:
IM = (-2 amps)

what does negative currents mean? flow the opposite direction?
A "negative current" means the computed current flows in the direction opposite to the direction defined to be the (+) direction when setting up the solution. For the middle branch (to which Im refers), the (+) direction was initially defined to be {Right-to-Left}. Thus, the actual computed current of (-2 amps) will flow {Left-to-Right}. The value of Im=(-2 amps) automatically indicates this and must be used whenever the middle branch current value is required in Kirchoff's Laws.
(Note: The (+) current direction can initially be defined in any direction that is convenient to solving the problem. However, once defined, this initial definition must always be maintained throughout the solution.)


~~
 
Last edited:

1. What is an electric circuit?

An electric circuit is a path for electrons to flow through, typically consisting of a power source, conductors, and loads. It allows for the transfer of electrical energy, which can be used to power devices and perform work.

2. What is the difference between series and parallel circuits?

In a series circuit, components are connected one after the other, creating a single pathway for current to flow. In a parallel circuit, components are connected side by side, creating multiple pathways for current to flow. This results in different overall resistance, voltage, and current values for each type of circuit.

3. How do I calculate resistance in a circuit?

Resistance (R) in a circuit can be calculated using Ohm's Law, which states that R = V/I, where V is the voltage and I is the current. Additionally, you can use the equation R = ρL/A, where ρ is the resistivity of the material, L is the length of the conductor, and A is the cross-sectional area of the conductor.

4. What is the purpose of a diode in a circuit?

A diode is a semiconductor device that allows current to flow in only one direction. It is often used in circuits to rectify AC voltage into DC voltage, since it only allows the positive portion of the AC waveform to pass through. Diodes can also be used for voltage regulation and signal processing.

5. How does a capacitor work in a circuit?

A capacitor is a device that stores electrical energy in the form of an electric charge. It consists of two conductive plates separated by an insulating material, and when connected to a power source, one plate accumulates a positive charge while the other accumulates a negative charge. This stored energy can then be released when the capacitor is connected to a load, making it useful for smoothing out voltage fluctuations in a circuit.

Similar threads

  • Introductory Physics Homework Help
Replies
3
Views
488
  • Introductory Physics Homework Help
Replies
3
Views
508
  • Introductory Physics Homework Help
Replies
14
Views
559
  • Introductory Physics Homework Help
2
Replies
42
Views
866
  • Introductory Physics Homework Help
Replies
4
Views
210
  • Introductory Physics Homework Help
Replies
1
Views
185
  • Introductory Physics Homework Help
Replies
6
Views
552
  • Introductory Physics Homework Help
Replies
21
Views
2K
  • Introductory Physics Homework Help
Replies
10
Views
810
  • Introductory Physics Homework Help
Replies
4
Views
825
Back
Top