# Series Circuit

#### boondock11

Joined Dec 20, 2006
5
Can anybody help me with this? I suck at this and everything about electronics so help would be much appreciated.

R1=47k Ir1=_______ Er1=______ Pr1=_______
R2=470k Ir2=_______ Er2=______ Pr2=_______
R3=_____ Ir3=_______ Er3=______ Pr3=1.52mw
R4=12k Ir4=_______ Er4=______ Pr4=______
R5=150k Ir5=_______ Er5=______ Pr5=.6mw

Rt=
Et=
It=
Pt=

Its just a series circuit.

#### boondock11

Joined Dec 20, 2006
5
Oh and if you are good at Parallel Circuits, can you please help me on this one too. ^=represents OHMS

R1=285.714k^ Ir1=______ Er1=_____ Pr1=_____ Rt=_____
R2=108.108k^ Ir2=______ Er2=_____ Pr2=_____ Et=_____
R3=320k^ Ir3=______ Er3=_____ Pr3=_____ It=_____
R4=449.438k^ Ir4=______ Er4=_____ Pr4=_____ Pt=3.2w
R5= 526.316k^ Ir5=______ Er5=_____ Pr5=_____

#### pebe

Joined Oct 11, 2004
626

#### boondock11

Joined Dec 20, 2006
5
If this helps, I know that if you do the square root of Power divided by resistance then it comes out to some really bad decimal for which you put it in the Volts. But I dont know how you would make it mV or just V. Its the same with both questions and all that I haven't filled in. I've tried the problems and have a million numbers but I dont know what is right if any are right.

#### Dave

Joined Nov 17, 2003
6,970

Series Circuits

Parallel Circuits

All the information you require to answer the questions is contained within the above two links. Post up your attempts and you will not only get the correct answers, but you may understand how you arrived at them.

Dave

#### Dave

Joined Nov 17, 2003
6,970
If this helps, I know that if you do the square root of Power divided by resistance then it comes out to some really bad decimal for which you put it in the Volts. But I dont know how you would make it mV or just V. Its the same with both questions and all that I haven't filled in. I've tried the problems and have a million numbers but I dont know what is right if any are right.
mV and V is the same units, however the "m" is an SI prefix indicating that the voltage V is a thousandth, i.e. mV = V/1000 (or more accurately mV = 10^-3V). In engineering, these prefixes ascend and descend in powers of 3 - for more information see Volume V - Chapter 1.

Dave

#### boondock11

Joined Dec 20, 2006
5
R1=47k Ir1=.042mA Er1=2v Pr1=.084mw
R2=470k Ir2=.004mA Er2=2v Pr2=.008mw
R3=2.631k Ir3=.76mA Er3=2v Pr3=1.52mw
R4=12k Ir4=.166mA Er4=2v Pr4=.333mw
R5=150k Ir5=.013 mA Er5=2v Pr5=.6mw
Rt=681.63k Et=2V It=.985mA Pt=2.545mw

I pretty sure I did the steps that I was suppose to do, but to me that does not look right at all. The Parallel Circuit is the same way. Down Below.

R1=285.714k^ Ir1=.088mA Er1=2.529v Pr1=.202mw Rt=50k^
R2=108.108k^ Ir2=.233mA Er2=2.529v Pr2=.589mw Et=2.529v
R3=320k^ Ir3=.790mA Er3=2.529v Pr3=1.997w It=12.653mA
R4=449.438k^ Ir4=5.627mA Er4=2.529v Pr4=.14230mw Pt=3.2w
R5= 526.316k^ Ir5=4.805mA Er5=2.529v Pr5=.12151mw
This really doesn't make any sense at all. Can somebody help me and also teach me this?

#### Dave

Joined Nov 17, 2003
6,970
R1=47k Ir1=.042mA Er1=2v Pr1=.084mw
R2=470k Ir2=.004mA Er2=2v Pr2=.008mw
R3=2.631k Ir3=.76mA Er3=2v Pr3=1.52mw
R4=12k Ir4=.166mA Er4=2v Pr4=.333mw
R5=150k Ir5=.013 mA Er5=2v Pr5=.6mw
Rt=681.63k Et=2V It=.985mA Pt=2.545mw

I pretty sure I did the steps that I was suppose to do, but to me that does not look right at all. The Parallel Circuit is the same way. Down Below.

R1=285.714k^ Ir1=.088mA Er1=2.529v Pr1=.202mw Rt=50k^
R2=108.108k^ Ir2=.233mA Er2=2.529v Pr2=.589mw Et=2.529v
R3=320k^ Ir3=.790mA Er3=2.529v Pr3=1.997w It=12.653mA
R4=449.438k^ Ir4=5.627mA Er4=2.529v Pr4=.14230mw Pt=3.2w
R5= 526.316k^ Ir5=4.805mA Er5=2.529v Pr5=.12151mw
This really doesn't make any sense at all. Can somebody help me and also teach me this?
Ok, two points to make with regards to series and parallel circuits:

1. In (purely) series circuits, the current through each device is the same.

1. In (purely) parallel circuits, the voltage across each device is the same.

So for the series circuit, Rt is correct (681.63k).

We can say:

P = (I^2)*R

Therefore, rearranging:

I = √(P/R)

Looking at the information given for resistor 5 (in your opening post):

Ir5 = √(0.6e-3/150e3) = 6.325e-5 A = 0.6325μA

I said above, In (purely) series circuits, the current through each device is the same, therefore:

Ir1 = Ir2 = Ir3 = Ir4 = Ir5

Happy so far?

Ok, you should now be able to work out all the other values using the following four equations:

I = V/R

P = VI

P = (V^2)/R

P = (I^2)*R

Have a go and post up your answers. We can deal with the parallel circuits after.

Dave

#### boondock11

Joined Dec 20, 2006
5
I'm using a calculator. So if I put in Ir1 * R1 to get E1, could I put in 6.325 times 47 to get the answer.

#### Dave

Joined Nov 17, 2003
6,970
I'm using a calculator. So if I put in Ir1 * R1 to get E1, could I put in 6.325 times 47 to get the answer.
Apologies for the lateness of my reply, no you need to use the Exp or E key:

- Type 0.635

- Press Exp or E depending on your calculator (this should produce two more zeros on the right)

- For 'μ' type "+/- 6"

- For 'm' type "+/- 3

- For 'k' type "3"

So you should find V1 = R1*I1 = 0.29845 V

You will need to be familiar with how SI prefixes work - see the wikipedia article which gives a decent coverage to this area. Stick with it, you are not a million miles away from it - believe me.

Dave