I know that voltage = current x resistance. I also know that power = voltage x current.
I am trying to figure out how to solve this simple circuit but I cant and its just annoying me!
http://www.flickr.com/photos/67259037@N0…
So far I know that the:
Total resistance = 1200 ohms
Total current = 25 milli amps
Total power of the circuit = 750 milli watts (rounded off)
I need to find out the voltage across each resistor (at least I think its each one) and then find the amount current flowing through each one before I can find out how much power each one is using.
If it helps, I know that the answers are:
R1 = 187 milli watts
R2 = 62.5 milli watts
R3 = 277 milli watts
R4 = 222 milli watts
I just dont know how to get these answers and I would like some help. Thanks guys!
I am trying to figure out how to solve this simple circuit but I cant and its just annoying me!
http://www.flickr.com/photos/67259037@N0…
So far I know that the:
Total resistance = 1200 ohms
Total current = 25 milli amps
Total power of the circuit = 750 milli watts (rounded off)
I need to find out the voltage across each resistor (at least I think its each one) and then find the amount current flowing through each one before I can find out how much power each one is using.
If it helps, I know that the answers are:
R1 = 187 milli watts
R2 = 62.5 milli watts
R3 = 277 milli watts
R4 = 222 milli watts
I just dont know how to get these answers and I would like some help. Thanks guys!
-
What is R1? Does 2k7 mean 2007?
I'm going to reverse engineer the value of R1 from the answers you gave. The same current is flowing through R1 and R2, and P = I^2 R. So R is proportional to P. R1/R2 = P1/P2 = 187/62.5. So R1 must be (187/62.5) * 900 = 2700 ohms. I would never have guessed that from the notation "2k7".
OK, now to your question. R1 and R2 are in series. That branch has a total resistance of 3500 ohms. The 30 V is the voltage across the combined resistance. So the current through that branch is 30 V/3600 ohm = 0.00833 amps.
The same 30 V is also across the R3-R4 branch, which has a resistance of 1800 ohms. So the current through that branch is 30/1800 = 0.0167 amps.
Since R1 and R2 are in series, the same current of 0.00833 is flowing through each one. So the voltage across R1 is 0.00833 * R1 = 22.5 V, the voltage across R2 is 0.00833 * R2 = 7.5 V (note they add up to 30 V), and the power dissipated in each one is 0.00833^2 * R1 and 0.00833^2 * R2.
You do the R3-R4 branch similarly.
What you have to keep in mind is what is the same in parts of circuits and what is not. Things in series have the same current flowing through them. Things in parallel have the same voltage across them. Voltages of things in series add up to the total voltage. Currents through branches in parallel add up to the total current.
I'm going to reverse engineer the value of R1 from the answers you gave. The same current is flowing through R1 and R2, and P = I^2 R. So R is proportional to P. R1/R2 = P1/P2 = 187/62.5. So R1 must be (187/62.5) * 900 = 2700 ohms. I would never have guessed that from the notation "2k7".
OK, now to your question. R1 and R2 are in series. That branch has a total resistance of 3500 ohms. The 30 V is the voltage across the combined resistance. So the current through that branch is 30 V/3600 ohm = 0.00833 amps.
The same 30 V is also across the R3-R4 branch, which has a resistance of 1800 ohms. So the current through that branch is 30/1800 = 0.0167 amps.
Since R1 and R2 are in series, the same current of 0.00833 is flowing through each one. So the voltage across R1 is 0.00833 * R1 = 22.5 V, the voltage across R2 is 0.00833 * R2 = 7.5 V (note they add up to 30 V), and the power dissipated in each one is 0.00833^2 * R1 and 0.00833^2 * R2.
You do the R3-R4 branch similarly.
What you have to keep in mind is what is the same in parts of circuits and what is not. Things in series have the same current flowing through them. Things in parallel have the same voltage across them. Voltages of things in series add up to the total voltage. Currents through branches in parallel add up to the total current.