Series circuit answers correct?

[confused12345]

Homework Statement

3 batteries: Vt= 40v+20v+10v = 70v
R1= unknown
R2= Unknown
R3= 10 ohm
I= unkown
The ones which I am looking for are:
I3=___
I1=___
V1= ___
R1=___
R2=___

Homework Equations

V=IR
I=V/R
R=V/I

The Attempt at a Solution

I3= 7a
I1= 7a
V1=70v
R1= 10 ohm
R2= 10 ohm
Diagram:

Is this correct?

 

[lewando]

Hard to say. Strike that--impossible to say. Need a circuit diagram, please.

 

[gneill]

There seems to be some problems with your results. You'll have to give some details on how you arrived at your answers. How did you determine i3 to be 7A?

 

[confused12345]

I used the equation I=V/R
70/10 ohm <--- since that was the only resistance already given?

 

[gneill]

I see. Well, presuming that the 70V you've quoted is the sum of the voltages shown for the battery and the voltages across R2 and R3, then that 70V is NOT across R3. It's the potential across R1, which you don't yet have a value for.

Your figure shows a voltage across R3. Why don't you use that voltage and that resistance to determine the current?

 

[confused12345]

So if I use
I=V/R
=20/10
=2a
That is the correct current? I was using the totals to find I the first time.

 

[gneill]

So if I use
I=V/R
=20/10
=2a
That is the correct current? I was using the totals to find I the first time.

Yes, that is the correct current. It is a direct consequence of Ohm's law applied to R3 where you are given both the value of the resistance and the voltage across it.