Halp with electricity! (1 Viewer)

[ohexploitable]

Was gonna post in Prelim section but it doesn't allow images

What's the electrical potential at the marked location? My answer is 6V but the answers say I'm wrong

Doesn't 18V go into the top branch, then 12V is used in the 8Ω resistor leaving 6V at the point?

 

[hscishard]

So gay, haven't covered that yet.
Gotta wait till first lesson back so we can continue with electricity

 

[hscishard]

Perhaps the energy goes the other way around?
The voltage divides by 2?

Lol that was just a speculation.

 

[ohexploitable]

dw, just asked dad, the answers are wrong

 

[hscishard]

Nice. You have a dad that can teach you the hsc.

 

[alcalder]

Each branch in a parallel circuit has the same voltage across it, so the voltage in the top branch IS 18V.

Now, you need to know the current in the top resistors.

R_{top branch}= 4 + 8 = 12 ohms

Thus
I_top = V/R_top = 18/12 = 1.5A

SO, the voltage across the 4ohm resistor is
V_4ohm = IR = 1.5 x 4 = 6 V

So, you are completely correct. What did the book say??

 

[ohexploitable]

The book said 12V, I think they made a mistake and did the opposite of conventional current.

 

[alcalder]

That would indeed be the correct answer IF the current were going in the other direction. Well done!

 

[hscishard]

Perhaps the energy goes the other way around?
The voltage divides by 2?

Lol that was just a speculation.

Ouch. Who is the man?!

 

[ohexploitable]

Ouch. Who is the man?!

lol, in HSC Physics current goes in the direction of the electric field, so you're incorrect

 

[hscishard]

lol, in HSC Physics current goes in the direction of the electric field, so you're incorrect

I was just saying, thats how they got 12V