- #1
Calculate Current Through R3: Negative Possible?
Click For Summary
Homework Help Overview
The discussion revolves around calculating the current through resistor R3 in a circuit, with a focus on the implications of obtaining a negative current value.
Discussion Character
- Exploratory, Assumption checking, Problem interpretation
Approaches and Questions Raised
- Participants discuss the legitimacy of a negative current and its meaning in terms of direction. There are questions about the correctness of loop equations and the potential changes across circuit elements.
Discussion Status
Some participants have provided guidance on interpreting negative current values and have pointed out potential issues with the original equations. There is ongoing exploration of the loop equations, with attempts to clarify the relationships between voltage and current in the circuit.
Contextual Notes
There are indications of confusion regarding the setup of loop equations and the direction of current flow, with references to specific voltage values and circuit elements that may not be fully detailed in the discussion.
- #2
lewando
Homework Helper
Gold Member
- 1,366
- 145
It is a legitimate answer provided you show a direction arrow (which you have done). It means that the current is not traveling in the direction indicated by your direction arrow. It is going in the opposite direction.
- #3
lewando
Homework Helper
Gold Member
- 1,366
- 145
Looking at your loop equations, they seem a bit suspect. If you are summing the changes in voltage across each element along a loop, equating the sum to zero, you should get something different.
- #4
ehild
Science Advisor
Homework Helper
- 15,536
- 1,917
Sastronaut said:
Your equations 1 and 2 are wrong. Note, that the potential decreases in the direction of the current.
ehild
- #5
Sastronaut
- 68
- 0
What should my equation for loop 1 be?
- #6
ehild
Science Advisor
Homework Helper
- 15,536
- 1,917
You start at the negative pole of the battery, and follow the change of potential in the direction, indicated by the green arrow. The potential increases by 5 V traversing the battery. Then it decreases by I3R3 along R3. Then again, it decreases by R1I1, when you return to your initial position. The net change of potential is zero: 5-I3R3-I1R1=0.
Do the same for the other loop. Note that going in direction opposite to the current, the potential would increase.
ehild
Do the same for the other loop. Note that going in direction opposite to the current, the potential would increase.
ehild
- #7
Sastronaut
- 68
- 0
okay I think I am following you so for loop 2 the equation is then -10V+I3R3+I2R2=0?
- #8
ehild
Science Advisor
Homework Helper
- 15,536
- 1,917
Sastronaut said:
Yes.
ehild
Similar threads
- · Replies 5 ·
- · Replies 4 ·
- · Replies 5 ·
- · Replies 11 ·
- · Replies 3 ·
- · Replies 4 ·