Basic Electric Potential Theory

In summary, the conversation discusses a basic theory involving capacitors and electric potential and the difficulty in finding the final voltage across a fully charged capacitor. The solution involves using V=IR and the concept of Kirchhoff's loop rule. This rule states that the voltage difference between two points in a circuit must be zero when moving from a point back to itself. Therefore, the voltage difference across the resistor and capacitor must be the same since they share the same two points.
  • #1
mcpoopants
1
0
Alright, so there is a very basic theory involving capacitors and electric potential that is throwing me off. I have a very basic problem here: http://img444.imageshack.us/img444/2251/73619554.png [Broken]

Assume the switch is closed and the capacitor is fully charged. From here I'm prompted to find the final voltage across the capacitor. Pretty obvious, you use V=IR, but I'm missing out on the value of "R". In this problem it is just R2, which is given to you. My problem is that I do not understand how the voltage across that resistor is equivalent to the voltage across that fully charged capacitor. It'd really help to explain as slowly as possible, because it is a basic idea that is kicking my butt in more complicated problems. Thanks to all.
 
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  • #2
Use kirchhoffs loop rule around R2 and the capacitor. When you move from a point in a circuit, back to the same point, the net voltage change must be zero. This is the same thing as saying that the voltage difference between a point and itself is zero.

So, if a point on the top wire---between the resistor and capacitor---has a given voltage difference from a point on the bottom wire---between the resistor and cap---across the resistor, it has to be the same as across the capacitor... because they're the same two points.

Does that make any sense?
 

1. What is electric potential?

Electric potential is the amount of electric potential energy that a charged particle has at a specific point in an electric field. It is measured in volts (V) and is a scalar quantity, meaning it has magnitude but no direction.

2. How is electric potential different from electric potential energy?

Electric potential energy is the amount of work required to move a charged particle from one point to another in an electric field. Electric potential, on the other hand, is the electric potential energy per unit charge at a specific point in the field.

3. What is the relationship between electric potential and electric field?

Electric potential and electric field are closely related. The electric field is the gradient of the electric potential, meaning it is the rate of change of electric potential with respect to distance. In other words, the electric field points in the direction of decreasing electric potential.

4. What is the equation for electric potential?

The equation for electric potential is V = kQ/r, where V is the electric potential, k is Coulomb's constant (8.99x10^9 Nm^2/C^2), Q is the amount of charge, and r is the distance from the charge. This equation is for a point charge, but can be extended to multiple charges using the principle of superposition.

5. How is electric potential used in practical applications?

Electric potential is used in many practical applications, such as in the design of electrical circuits and in calculating the energy required for an electric motor to operate. It is also used in medical devices, such as electrocardiograms and defibrillators, to measure and control electrical activity in the body.

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