Charging a Capacitor: Battery & Conductor Effects

In summary, when you connect a battery to a capacitor, the capacitor becomes charged. The process of charging the capacitor happens concurrently with the movement of electrons from the battery to the capacitor. Something prevents the electrons from moving from the positive terminal to the negative terminal.
  • #1
henry3369
194
0
I need some clarification on batteries and capacitors.

Before a battery is connected to a capacitor, the capacitor is uncharged. When a battery is connected, an electron from one conductor moves toward the positive terminal of the battery, leaving this conductor positively charged. What causes the other conductor to become negatively charged? At this point, the positive terminal loses charge because it has an additional electron. The other conductor is still neutral at this point and something has to cause an electron from the negative terminal to move to the neutral conductor.
 
Physics news on Phys.org
  • #2
The battery moves electrons from one side of the capacitor to the other...
henry3369 said:
What causes the other conductor to become negatively charged?
... electrons get added to it.

At this point, the positive terminal loses charge because it has an additional electron.
... of the battery? The + terminal loses electrons, they get transferred to the - terminal.

The other conductor is still neutral at this point and something has to cause an electron from the negative terminal to move to the neutral conductor.
The neg terminal is negatively charged, so it repels electrons.
Like charges on a conductor - which is the neg terminal, the wire, and the capacitor plate, all together - try to get as far away from each other as possible.
 
  • #3
Simon Bridge said:
The battery moves electrons from one side of the capacitor to the other...
... electrons get added to it.

... of the battery? The + terminal loses electrons, they get transferred to the - terminal.

The neg terminal is negatively charged, so it repels electrons.
Like charges on a conductor - which is the neg terminal, the wire, and the capacitor plate, all together - try to get as far away from each other as possible.
Doesn't something prevent the electrons from moving from the positive terminal to the negative terminal? If not, how would the two terminals have opposite charges to begin with?
 
  • #4
The battery uses a chemical energy store to move charges from the positive side to the negative side.
The exact mechanism varies from battery to battery

Think of the electrons being like water and the battery is a pump moving water from a low reservoir to a high one. What prevents the water from flowing back down?
 
  • #5
A battery is not a gun that can just shoot electrons. It is important that you understand that for every single electron that comes out of the negative terminal of the battery, an electron must go into the positive terminal at the same time (at least for an ideal battery). If you were to look at a sketch the electric field lines for this circuit, you would see why. The positive end of the battery pulls electrons just as much as the negative end pushes electrons. Remember, there are always electrons at all parts of the circuit, since everything is made of atoms which contain both protons and electrons.

When a battery is connected to a cap, electrons are added to one plate, making that plate negative, and removed from the other plate, making that plate positive. These happen concurrently.
 
  • #6
OmegaKV said:
When a battery is connected to a cap, electrons are added to one plate, making that plate negative, and removed from the other plate, making that plate positive. These happen concurrently.

yes, and to follow on from that, to the OP, the voltage source doesn't charge a capacitor, it energises a capacitor
The net charge in a capacitor is always zero

Dave
 

1. How does a capacitor charge?

A capacitor charges by accumulating electrical charge on its parallel plates, creating an electric field between them. This field stores energy in the form of potential energy.

2. What is the role of a battery in charging a capacitor?

A battery is the source of electrical energy that allows a capacitor to charge. It provides the potential difference needed for electrons to flow from one plate to the other, creating the electric field.

3. How does a conductor affect the charging of a capacitor?

A conductor, such as a wire, is needed to connect the battery and capacitor in a circuit. It allows the flow of electrons from the battery to the capacitor, allowing it to charge.

4. What is the equation for calculating the charge on a capacitor?

The equation for calculating the charge on a capacitor is Q = CV, where Q is the charge in coulombs, C is the capacitance in farads, and V is the potential difference in volts.

5. What happens to the voltage across a capacitor as it charges?

As a capacitor charges, the voltage across it increases until it reaches the same potential as the battery. Once the capacitor is fully charged, the voltage across it will be equal to the battery's voltage.

Similar threads

  • Electromagnetism
Replies
16
Views
448
  • Electromagnetism
2
Replies
36
Views
2K
  • Electromagnetism
Replies
15
Views
873
  • Electromagnetism
Replies
4
Views
1K
Replies
4
Views
937
  • Electromagnetism
Replies
2
Views
10K
Replies
19
Views
3K
  • Electromagnetism
Replies
14
Views
1K
  • Electromagnetism
Replies
4
Views
877
  • Electromagnetism
Replies
2
Views
867
Back
Top