You are Here: Home >< Physics

# Capacitors

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. Please could someone explain the following questions:

When a capacitor discharges, why doesn't the current go round and attract to the other plate, charging the capacitor again?

When a capacitor has fully discharged, what does the charge configuration look like? Is there just extremely little negative charge on the plates at this point?

Does the Q in the capacitor discharge equation relate to the amount of negative charge on the plates, or both the negative and the positive?

Sorry if these questions are factually incorrect, but help would be much appreciated!
2. (Original post by PhyM23)
Please could someone explain the following questions:

When a capacitor discharges, why doesn't the current go round and attract to the other plate, charging the capacitor again?

When a capacitor has fully discharged, what does the charge configuration look like? Is there just extremely little negative charge on the plates at this point?

Does the Q in the capacitor discharge equation relate to the amount of negative charge on the plates, or both the negative and the positive?

Sorry if these questions are factually incorrect, but help would be much appreciated!
No. The current actually decreases the charge on the other side. Picture electrons moving off of the negative plate, around the circuit and onto the positive plate, decreasing the charge on the positive plate.

When it's fully discharged both plates are neutral. If it's charged and left to discharge then, using a continuous approximation, it won't actually be fully discharged in a finite amount of time so the language can be bent slightly to consider a very small charge as roughly discharged.

The magnitude of the charge on one of the plates. Either the positive or negative plate. It can also be considered as the charge that has moved from one plate to the other, with both plates starting as neutral.
3. (Original post by morgan8002)
No. The current actually decreases the charge on the other side. Picture electrons moving off of the negative plate, around the circuit and onto the positive plate, decreasing the charge on the positive plate.

When it's fully discharged both plates are neutral. If it's charged and left to discharge then, using a continuous approximation, it won't actually be fully discharged in a finite amount of time so the language can be bent slightly to consider a very small charge as roughly discharged.

The magnitude of the charge on one of the plates. Either the positive or negative plate. It can also be considered as the charge that has moved from one plate to the other, with both plates starting as neutral.
This is just what I was looking for. Thank you very much

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
your full birthday is required
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 20, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

### Who would you like to thank?

Poll
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.