Circuit Q Basics: Understand Electrical Circuits

  • Thread starter User1265
  • Start date
  • Tags Tags
    Circuit
5 replies · 2K views · last reply
User1265
Messages
29
Reaction score
1
Homework Statement
Image insert.
Are the two resistors in series or Parallel? and why so?
Relevant Equations
V=IR
2019-10-07.png
 
Attachments
  • Circuit schematic labelled (i): an ammeter A in series with a 20 V battery and a 4 Ω resistor on the top branch, with a 6 Ω resistor on the bottom branch, the two branches joined at dot junctions on the left and right.
    2019-10-07.png
    25.9 KB · Views: 246
As per our Forum rules you must make an effort to answer the question before you can receive help. Tell us what you think.
 
Recall Kirchhoff's current law, the sum of currents flowing into a node is equal to the sum of currents flowing out of it. Two resistors are said to be in series if they are siege to the same current, otherwise they are parallel.
Your circuit is a bit special, however. The wire connecting the two poles of the ##6\,\Omega## resistor short-circuits it because it is considered to be a ##0\,\Omega## resistor, as a result of which we theoretically assume that all the current will pass through it and none will pass through the bottom resistor. You might ask why this is, and I'll answer : compute the equivalent resistance with ##R_1=6\,\Omega## and ##R_2=0\,\Omega## and you'll find it to be ##0\,\Omega##.
Circuit diagram labelled (i): an ammeter A and a 20 V battery in series on the top branch, a 4 Ω resistor on the right, a 6 Ω resistor on the bottom, and a hand-drawn 0 Ω wire across a middle branch between the two nodes.
 
Last edited:
  • Like
Likes   Reactions: User1265
"compute the equivalent resistance with ##R_1=6\,\Omega## and ##R_2=0\,\Omega## and you'll find it to be ##0\,\Omega##."

Thank you! I forgot the zero resistance, but I don't understand the instructions quoted above, explaining as to why no current will pass though the 6 ohm resistor
 
kuruman said:
As per our Forum rules you must make an effort to answer the question before you can receive help. Tell us what you think.
I thought 6 ohm and 4 ohm were parallel since they shared the same two nodes, but I'm not sure if this is even the correct reason, as there is a battery between in the upper branch opposite the diagonal branch.
 
User1265 said:
I thought 6 ohm and 4 ohm were parallel since they shared the same two nodes, but I'm not sure if this is even the correct reason, as there is a battery between in the upper branch opposite the diagonal branch.
For future reference, something like this belongs in your original post under "Attempt at a solution".
User1265 said:
"compute the equivalent resistance with ##R_1=6\,\Omega## and ##R_2=0\,\Omega## and you'll find it to be ##0\,\Omega##."

Thank you! I forgot the zero resistance, but I don't understand the instructions quoted above, explaining as to why no current will pass though the 6 ohm resistor
The 6 ohm resistor is in parallel with the short (0 ohm resistor). When the current reaches the node, it will take the path of least resistance. In this case all the available current will go through the short.
 
Last edited:
  • Like
Likes   Reactions: User1265