How to Solve Tough Circuit Questions: Current, Power, and Graphing Tricks

[scorpa]

Hello there!

I am doing a really tough physics question on circuits. I am posting link to the picture of the circuit so you can actually see what is going on


These are the questions:

a) What is the current through R1?

This one was easy I just found the total resistance of the circuit and used the equation V= IR to get a current of 2.4 A which is the answer/

b) What is the current through R4?

I have no clue how to do this one, no matter what I do I get an answer either to high to to low. The answer should be 0.8 A.

c) What is the power dissipated in R2?

I have a feeling that I can't get this one because I can't get the one before it. The answer should be 5.1W.

d) What is the total power dissipated in the circuit?

I could do this one. It's just p = iv (12.0V)(2.4A) = 29W



Oh and one more really stupid thing. When you are drawing a graph and it says to plot resistance as a function of the cross-sectional area the resistance should go on the x-axis right?

 

[GCT]

you've forgot the link

 

[thepatientmental]

Hi there! Solving circuit questions can definitely be tough, but with a few tricks and techniques, you'll be able to tackle them with ease.

For question b), the key is to use Ohm's Law (V=IR) and the concept of parallel resistors. Since R2 and R3 are in parallel, they have the same voltage drop across them. This means that the current through R4 will be the same as the current through R2 and R3 combined. So, we can calculate the total resistance of R2 and R3 (1.5 ohms) and use that with the given voltage (12V) to find the total current through both resistors (8A). Since R4 is in series with this combination, the current through R4 will also be 8A. From there, you can use Ohm's Law again to find the voltage drop across R4, and then use that to find the current through R4 (0.8A).

For question c), you can use the same approach as question b) to find the current through R2 and then use power formula (P=I^2R) to find the power dissipated in R2.

And for the graphing question, yes, resistance should be on the x-axis since it is the independent variable.

Hope this helps and good luck with your circuit questions!