Resistors in Parallel Help

[Markrobert30]

Hi All first post.

I'm currently doing a Pre Entry in Electrical Engineering and really enjoying it so far.
My question is i'm finding the Resistors in Parallel a bit tricky see below.

The question asks me to determine the values of V,I2,I3 and R

Suppose i'm more confused in whats best to workout first

I've attached a Jpeg of it so you can see it i've written in the answers as they were on the sheet but if anyone could help i'd be really grateful.

Image below also.

Thanks

Mark

 

[Sintra]

This isn't really working out resistance in parallel more a case of ohms law.
First thing I would work out is V using the value of R1 and the current across it. V = I x R,
V = 10 x 5 so V = 50.
Then knowing the voltage you can work out the current I2 using I = V / R, I = 50 / 10 so I2 = 5A.
Lastly for I3 you know you had 40A to start with and you have 10A across R1 and 5A across R2 leaving you 25A across R3. Then use R = V / I, R = 50 / 25 so R = 2 ohms.

Hope this helps.

 

[Markrobert30]

This isn't really working out resistance in parallel more a case of ohms law.
First thing I would work out is V using the value of R1 and the current across it. V = I x R,
V = 10 x 5 so V = 50.
Then knowing the voltage you can work out the current I2 using I = V / R, I = 50 / 10 so I2 = 5A.
Lastly for I3 you know you had 40A to start with and you have 10A across R1 and 5A across R2 leaving you 25A across R3. Then use R = V / I, R = 50 / 25 so R = 2 ohms.

Hope this helps.

Hey Sintra

That's perfect thank you think i was just getting myself confused with what to workout first. But your workings make it look so easy.

Mark

 

[happysteve]

This isn't really working out resistance in parallel more a case of ohms law.
First thing I would work out is V using the value of R1 and the current across it. V = I x R,
V = 10 x 5 so V = 50.
Then knowing the voltage you can work out the current I2 using I = V / R, I = 50 / 10 so I2 = 5A.
Lastly for I3 you know you had 40A to start with and you have 10A across R1 and 5A across R2 leaving you 25A across R3. Then use R = V / I, R = 50 / 25 so R = 2 ohms.

Hope this helps.

<pedant> Current flows through a resistor, not across it eg "you have 10A flowing through R1." You have a voltage across summat, eg "you have 50V across R3, and you know there's 25A flowing through it, so R3 = V / I = 50 / 25 = 2 Ohms." </pedant>

Other than that, absolutely spot on