Capacitance Problem

[yashrs]

Please guide me for finding the equivalent capacitance for the given problem attached.

[Mordred]

First seperate the pathways into series and parallel paths.

 

Then apply the series and parralel capacitance addition equations to each pathway circuit.

 

Add the resultance together for the total capacitance.

 

Series.

 

[latex]c_t=\frac {1}{c_1}+\frac{1}{c_2}...[/latex]

 

Parallel

 

[latex]c_t=c_1+c_2...[/latex]

Edited May 31, 2015 by Mordred

[yashrs]

First seperate the pathways into series and parallel paths.

 

Thats the more of a problem for me. In which way do I separate it ? I really get confused in this type of problems. Any help on this please

Edited May 31, 2015 by yashrs

[studiot]

I assume you mean the reduced capacitance between the points A and B?

 

Pick either point A or B (I suggest B) and rederaw the circuit on a rectangular grid, with A at the top and B at the bottom.

 

The relationships should become apparent then.

 

Have a go and I will post my version in about half an hour.

Here is how to build it up.

 

Can you see what comes next?

 

 

 

[Mordred]

Good methodology , being used to mnemonics I would of suggested a less obvious method.( lol I tend to think in terms of Boolean logic circuits)

Yours is the better and more suited methodology.

(I will leave this in your more than capable hands)

Edited June 1, 2015 by Mordred

[yashrs]

Here is how to build it up.

 

Thank you, it really helped

After getting the 1 C and the 2 C capacitors in parallel :-

Then which two capacitors should I take in parallel and which in series ? Thanks for the help.

Edited June 1, 2015 by yashrs

[studiot]

Well I was hoping you would see that the 17 and 13 capacitors are in the same situation as the 1 and 2.

 

Incidentally it is good to use the units, but do get the correct ones.

 

Capacitors are measure in Farads., not Siemens, which is a unit of conductance.

 

(Mostly we work in milli, micro and nano farads)

[yashrs]

You mean that the 17 and the 13 capacitors are in parallel ? How ? The potential difference wouldn't be same AFAIK.

[studiot]

OK so we need to review what parallel means.

 

(We can do the series after since the next stage will be a series combination, in case you are pining for one.)

 

Capacitors have two terminals. Call them A and B and the capacitors ! and 2.

 

If we have two such with terminals devices {1A , 1B} for device 1 and {2A , 2B} for device 2 and

 

Directly connect the A terminals together and the B terminals together

 

The devices are connected in parallel.

 

So 1A is connected to 2A and 1B is connected to 2B, directly.

 

 

************************************************************************************************************

 

 

Now if we reverse on of the devices so that

 

So 1A is connected to 2B and 1B is connected to 2A, directly.

 

The devices are said to be connected in anti-parallel.

 

For most capacitors it does not matter which way round we connect or which we consider to be the A terminal and which we consider to be the B terminal.

But for some devices it does matter and this includes some capacitors. Such devices are called polarised. (polarized in American).

Other polarised devices like this include diodes.

 

***********************************************************************************************************************************************************

 

So look carefully at the diagram.

 

Can you see that in the original the 1 and 2 capacitors had their AA and BB terminals tied togerther and that is the same for the 13 and 17 caps?

 

So replace the 13 and 17 with their parallel equivalent.

 

Can you now see a simple series combination as a result of that substitution?

 

Hint it should be a 30 in series with a 5.

Edited June 1, 2015 by studiot

[yashrs]

OK so we need to review what parallel means.

 

Thank you so much for explaining me in such detail !! It really helped !! I was finally able to solve it.

[studiot]

 

yashrs

I was finally able to solve it.

 

For you to be able to say that is the purpose of the homework help.

 

Now you understand what you are doing and have a sound systematic method for future problems.