Capacitors and Capacitance

Describes what is and what affects capacitance. Introduces the parallel plate capacitor and equivalent capacitance, discusses the dielectric constant and explains energy stored in a capacitor. Solved examples. IB Physics Topic 11.3
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Table of Contents
0:00 A battery connected to plates
6:12 One of these in not like the others
7:13 Capacitance formula
9:53 Solved Example
12:34 Parallels between equivalent resistance and equivalent capacitance
14:34 Physical Explanation
17:02 Solved Example
18:29 Energy stored in a Capacitor
21:29 Energy Problem example
27:15 Summary

[@rishitsharma279]

Best IB channel

[@donerphysics]

I hope so. Thank you.

[@armaandurani7728]

out here 3 days before my physics hl boards!

[@shikharmukherji1236]

At 10:46 I think the unit conversion should be a division by 100^2, not a multiplication

[@donerphysics]

clearly yes, thank you.

[@shadowdestroyer5033]

23:17 the problem states 24 uC of charge on EACH plate. Now wont that mean (based on the sign of a capacitor) that capacitor A will have 48uC of charge since it has 2 plates? Or are the signs purely representational and we treat all capacitors as having only one plate?

[@donerphysics]

The charge on the plates is equal and opposite. The charge referred to on a capacitor is the charge on each plate. We are effectively saying how much charge has been separated.

[@gabrielalexandreacostaperd2497]

For question c I tried using E = 1/2*C*V^2, but I got the wrong answer. Could you explain? Btw, I got V by dividing q/C, so 24/12, which equals 2V.

[@myronchan8568]

for 11:20 I got 1.3 * 10^-10, was there a calculation error because i inputted the exact values from the videos

[@alankritachavan4253]

Hi sir, you said that to increase the capacitance we can increase the voltage supplied at 1:57, but the capacitance equation is C = Q/V (8:06) so according to the equation doesn't that mean if you increase the voltage you decrease the capacitance due to the inverse relationship?

[@donerphysics]

In the first instance voltage increased charge not capacitance.

[@achint8244]

Hello, Do we have Capacitor Rectification for the finals? If there is, do you have a video on it?

[@donerphysics]

You mean rectification with diodes, and perhaps a capacitor. See the review video.

[@achint8244]

@@donerphysics alright, thank you

[@ashar4121]

At 25:00, how are the capacitors connected in parallel?

[@donerphysics]

I understand the question since the two capacitors in the problem are connected in a loop, so it is kind of parallel and series at the same time. Generally, parallel for capacitors is the same as for resistors. The difference is that for capacitors, voltage is the same in parallel and charge splits, Charge is the same in series and voltage splits.

[@christopherjiang30]

How do we know if a capacitor is connected in series or parallel?

[@donerphysics]

The wires must branch so a parallel connection (typically the capacitors are side by side). In series the wire does not branch and the capacitors typically look like one after the other.

[@aashikotecha3785]

@@donerphysics In the problem at 24:17, the question says the capacitors are connected in series?

[@donerphysics]

There are no forks in the path. For parallel, the current must have a choice as to where it can flow through.

[@krishakalsi6384]

@@donerphysics why have we assumed the capacitors to be connected in parallel for the b part then?