Why is the problem impossible. He is given the current in the unknown resistance, not the total current. The key is in recognizing what the voltage is across that resistance if they are all in parallel (as indicated by the thread title).After having run the numbers - I don't believe your resistors are in parallel. I bet you mean to say "In Series".
Parallel resistors will ALWAYS have a lower resistance than the smallest resistor. For instance, two 100Ω resistors in parallel will have a resistance of 50Ω. Even if one of those two resistors are in the meg ohm range, the resistance will be less than the smallest, 100Ω resistor. So the problem as you present it is impossible. Unless I got something horribly wrong.
Which implies that the values of R1 and R2 are irrelevant... so why give them?Why is the problem impossible. He is given the current in the unknown resistance, not the total current. The key is in recognizing what the voltage is across that resistance if they are all in parallel (as indicated by the thread title).
To see if the student can recognize that they are irrelevant to the question asked.Which implies that the values of R1 and R2 are irrelevant... so why give them?
And what if the TS is confused as to what parallel (or serial) means? Your previous comment (and my reply) only makes sense if the resistors are wired in serial.Look at the thread title.
I considered that as well...To see if the student can recognize that they are irrelevant to the question asked.
The problem makes perfect sense if they are wired in parallel (or in series). You can solve it either way, you just get different values for the resistance since the voltage across it is different in each case.And what if the TS is confused as to what parallel (or serial) means? Your previous comment (and my reply) only makes sense if the resistors are wired in serial.
After having run the numbers - I don't believe your resistors are in parallel. I bet you mean to say "In Series".
Parallel resistors will ALWAYS have a lower resistance than the smallest resistor. For instance, two 100Ω resistors in parallel will have a resistance of 50Ω. Even if one of those two resistors are in the meg ohm range, the resistance will be less than the smallest, 100Ω resistor. So the problem as you present it is impossible. Unless I got something horribly wrong.
How do you figure out the total resistance in a parallel circuit given the following information:
voltage: 150VDC
IR3: 2.5 amps
R1: 20 ohms
R2: 30 ohms
R3: ? (Not provided)
voltage: 150VDC
IR3: 2.5 amps
I missed IR3 being 2.5A. After realizing that from the full diagram and full question I was able to figure it out. I was assuming 2.5A through the entire circuit. My mistake. If the total current were 2.5A then there would be no resistor value large enough to account for the numbers. That was why I thought initially that the resistors could not be parallel. Sorry for adding to the confusion.Why is the problem impossible. He is given the current in the unknown resistance, not the total current.
LoLAre they wired like this?
View attachment 224132
Or like this?
View attachment 224133
(Excuse the crappy graphics)
You actually don't need to find what R3 is at all.I attached the picture of the question. The possible answer choices are
2250 watts
1500 watts
375 watts