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Original post by Jail_break
Hi guys. I'm struggling a lot to solve c4a.9 (parts B and C) on Isaac physics.

Here is the link to the question: https://isaacphysics.org/questions/phys19_c4a_q9?board=phys19_c4_add&stage=a_level

If anyone could help me that would be great!


For part B, there are at least 2 methods of finding the current.
The first method is to find the total resistance of the circuit.
The second method is to find the current in 3R and 4R resistors respectively and then sum them up.

For part B, use part A answer to find the voltage across the R resistor.
Then use the power formula V^2/R to find the power dissipated in the R resistor.
Original post by Jail_break
Hi guys. I'm struggling a lot to solve c4a.9 (parts B and C) on Isaac physics.

Here is the link to the question: https://isaacphysics.org/questions/phys19_c4a_q9?board=phys19_c4_add&stage=a_level

If anyone could help me that would be great!


Hello, any chance you have the answer to part a?
try redrawing the circuit so that there are two branches (one branch only containing the 3R resistor, and the other branch containing 2 1R, and 1 3R in parallel with the 4R being in series with them)
As the voltage across the two branches is the same, to find the potential difference across the 4R resistor, you use the potential divider equation to find out the voltage across the 4R resistor.


Spoiler



Original post by yeyenono1301
Hello, any chance you have the answer to part a?
(edited 6 months ago)
Reply 4
I tried this for part B and im not sure why ? I ended up getting 93/52 for the combined resistance ?
Original post by oliver.s.
I tried this for part B and im not sure why ? I ended up getting 93/52 for the combined resistance ?

I think you mean 9352R \frac{93}{52} R which is correct. Good. :smile:
Original post by oliver.s.
I tried this for part B and im not sure why ? I ended up getting 93/52 for the combined resistance ?

If you want to ask more questions please use the thread that you have started.
https://www.thestudentroom.co.uk/showthread.php?t=7437427
Because we will close this old thread soon.

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