- #1
physics user1
Homework Statement
Why in a circuit in parallel I can't use P= i^2 R where R is the equivalent resistance? Why do I have to use P= V^2/R ?
Dissipated in resistance,CWatters said:Please give an example circuit. Power dissipated in what?
I dunno. Why do you think you cannot? Can you post a diagram of the circuits?Cozma Alex said:Homework Statement
Why in a circuit in parallel I can't use P= i^2 R where R is the equivalent resistance? Why do I have to use P= V^2/R ?
Homework Equations
P= Vi , P= V^2/R , P= i^2R[/B]The Attempt at a Solution
berkeman said:I dunno. Why do you think you cannot? Can you post a diagram of the circuits?
I'm not able to see your very dim attachment.Cozma Alex said:Why in a circuit in parallel I can't use P= i^2 R where R is the equivalent resistance? Why do I have to use P= V^2/R ?
Yes I knew that, but I thought that calculating the total resistance is was able to "transform" each circuit into one with one resistance with a current i like that: (photo)berkeman said:I'm not able to see your very dim attachment.
Are you familiar with how current divides into parallel circuits? Maybe that's the disconnect here. For parallel circuits, the voltage is the same but the current flows through both parallel branches...
Quite so. Reducing the parallel resistors to an equivalent single resistance allows you to work out the total current, but it does not tell you how much of that flows in each. The two individual currents will be in inverse proportion to the resistances.Cozma Alex said:Then other approach that I had thinking at the problem was thinking that maybe i would have been different in each circuit
haruspex said:The two individual currents will be in inverse proportion to the resistances.
yes, you can do it that way, but it is simpler just to apply V2/R to each in the first place.Thewindyfan said:So for this problem -I'm just assuming so don't take this to be an answer OP - but isn't it basically finding information from simplifying the current to have an equivalent resistance then applying that newfound info to the individual branches?
Ah okay, I'll look into that formula. Do you know what this equation is known as/called? I'd like to look into how this is derived because it's not immediately apparent to me at the moment.haruspex said:yes, you can do it that way, but it is simpler just to apply V2/R to each in the first place.
V2/R? You can derive it from V=IR and P=IV.Thewindyfan said:Ah okay, I'll look into that formula. Do you know what this equation is known as/called? I'd like to look into how this is derived because it's not immediately apparent to me at the moment.
Thanks! I'll do that now and work it through.haruspex said:V2/R? You can derive it from V=IR and P=IV.
P=I2R. Put I=V/R. Voltage is same across parallel resistors. So, power will be inversely proportional to the resistance value.Thewindyfan said:Ah okay, I'll look into that formula. Do you know what this equation is known as/called? I'd like to look into how this is derived because it's not immediately apparent to me at the moment.
Thanks, thought there was more to it than there actually is haha.cnh1995 said:P=I2R. Put I=V/R. Voltage is same across parallel resistors. So, power will be inversely proportional to the resistance value.
It works fine if V is the voltage across the entire branch and R the total resistance of the branch.Cozma Alex said:Does P= V^2/R works also for series circuits? In series i is constant and V vary right?
V^2/R and i^2R are both equations used to calculate power in parallel circuits. V^2/R represents the power dissipated by the individual resistors in the circuit, while i^2R represents the power dissipated by the entire circuit as a whole.
It depends on what you are trying to calculate. If you want to know the power dissipated by each individual resistor, use V^2/R. If you want to know the total power dissipated by the circuit, use i^2R.
As the resistance in a parallel circuit increases, the power dissipated by each individual resistor (V^2/R) decreases. However, the total power dissipated by the circuit (i^2R) remains the same.
No, V^2/R and i^2R are only applicable to parallel circuits. In a series circuit, the power can be calculated using the equation P = i^2R, where i is the current and R is the total resistance of the circuit.
By manipulating the resistance values in a parallel circuit, you can adjust the power dissipated by each individual resistor (V^2/R) to achieve a desired overall power dissipation (i^2R). This can help optimize the efficiency and performance of your circuit.