# Three dielectric slabs in a capacitor

1. Feb 13, 2016

### gracy

My textbook says this makes three pairs of parallel capacitors.
I don't understand how?To make three pairs of parallel plates capacitors we at least need four plates but here we have only two

2. Feb 13, 2016

### cnh1995

You can insert metal plates at the boundaries of two dielectrics. They will be equipotential. Then splitting each plate into two plates in series, you can have 6 plates i.e. 3 capacitors.

3. Feb 13, 2016

### gracy

I think we need only four plates to form three parallel plate capacitors.

4. Feb 13, 2016

### cnh1995

Yes. But to distinguish three separate capacitors, you can make six plates from them.

5. Feb 13, 2016

### gracy

So we do need to insert metal plates there otherwise it is not possible to have 3 pairs of capacitors.

Here I have shown green and orange metal plates placed at boundaries of dielectric slab . The left most and the right most plates were already there.

6. Feb 13, 2016

### cnh1995

Even if you don't insert plates, still it is a 3 capacitors in series combination.

7. Feb 13, 2016

### gracy

How?That is all my OP about.

8. Feb 13, 2016

### SammyS

Staff Emeritus
How _____what_____ ?

9. Feb 13, 2016

### gracy

To make three pairs of parallel plates capacitors we at least need four plates.

10. Feb 13, 2016

### cnh1995

11. Feb 13, 2016

### SammyS

Staff Emeritus
See post #2.

What is he not clear about.

12. Feb 13, 2016

### gracy

He is also talking about inserting metal plates .

13. Feb 13, 2016

### cnh1995

See mentor NascentOxygen's post #14 in that thread.

14. Feb 13, 2016

### gracy

At that time also I was having same doubt. But I tried to focus on different aspect of that problem.

15. Feb 13, 2016

### SammyS

Staff Emeritus
16. Feb 13, 2016

### cnh1995

What is not clear about that post?

17. Feb 13, 2016

### gracy

18. Feb 13, 2016

### gracy

I don't understand how is it relevant to being "equipotential"?

19. Feb 13, 2016

### SammyS

Staff Emeritus
Do you see that each boundary between the dielectric slabs is an equipotential surface?

20. Feb 13, 2016

### gracy

No. Is it perpendicular to electric field lines ?

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