capacitors

i missed the 2 lessons we had on capacitors (our lessons are 2 hours and 20 minutes long each so that is a LOT) due to university interviews and such. i have the main idea behind capacitors grasped. the problem is that my teacher was telling me briefly about things flowing from both sides of the battery which didn't quite make sense. also, i have a scenario where i have a battery, a capacitor and 2 ammeters on both ends. when the wires are connected to the battery and the capacitor is charging, what is the trend in current on both sides of the circuit?

Reply 1

Oddball

As a capacitor charges, the current flowing decreases exponentially. This can be observed by setting up a capacitor (with a resistor in the circuit, otherwise it will discharge very quickly.)

Capacitors store charge - negative on one plate, and positive on the other. You can then discharge the capacitor, and use it as a power source.

A few things to take note of, Capacitance is measured in F, Farads (though they are usually micro or pico Farads).

Charge = Capacitance * Volts

or

Q = CV

And the Energy stored in a capacitor is given by

E = 1/2 cv^2

The electric field strength between two plates (i.e. a capacitor) is given by

E = volts / distance.

Hope this helps!

Reply 2

madima

yep those were about all the fundemental ideas i found. now what about that circuit problem that i mentioned? that's still confusing me...

Reply 3

teachercol

Both meteres read the same. Current decays exponentially.

Reply 4

madima

teachercol

Both meteres read the same. Current decays exponentially.

...why?

Reply 5

tillhm

madima

...why?

Imagine the wires to be a garden hose. Unless there is some hole in your hose the exact same amount of water (or charge) will flow through the hose no matter where you measure the "current"