Electrical Potential Energy

In summary, the total voltage supplied to an electrical series circuit will equal the sum of the potential drop across the circuit. This means that when a battery is connected to a circuit, the sum of the voltage drops around the loop will equal the applied potential difference. Even if there are no electrical devices in the circuit, the battery still has an internal resistance that limits the short circuit current. In terms of Ohm's Law, when the resistance is zero, the current will be infinite and the voltage across the circuit can be any value, including 12V. It is important to remember to model real world components in terms of ideal elements to better understand and analyze circuits.
  • #1
danago
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Hey. I've been told that the total voltage supplied to an electrical series circuit will equal the sum of the potential drop across the circuit. I am a bit confused.

Lets say i have a 12V battery in a circuit, so each coulomb of charge obtains 12J of potential energy. What if there are no electrical devices? How can the potential drop equal the supplied potential difference?
 
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  • #2
I'm not quite sure, but if there were no electrical devices in the circuit, wouldn't that mean that there is zero potential drop?
 
  • #3
Well, yes. But then you don't really have a circuit since you need some sort of resistor to make your circuit non-trivial.
 
  • #4
A power source give you a voltage increase, and current flowing through loads gives you voltage drops. When you have a battery sitting there open circuit, there is no external current flow, so all you have is the battery voltage. When you connect it to an external circuit (like say two resistors in series), the sum of the voltage drops will equal the applied potential. So if you add up the voltage drops going around a complete loop, you get a negative voltage drop (voltage increase) at any sources, and positive drops at loads. The sum around the loop will equal zero.
 
  • #5
berkeman said:
A power source give you a voltage increase, and current flowing through loads gives you voltage drops. When you have a battery sitting there open circuit, there is no external current flow, so all you have is the battery voltage. When you connect it to an external circuit (like say two resistors in series), the sum of the voltage drops will equal the applied potential. So if you add up the voltage drops going around a complete loop, you get a negative voltage drop (voltage increase) at any sources, and positive drops at loads. The sum around the loop will equal zero.

Yes, if you need further explanation look up Kirchoff's Voltage Law.
 
  • #6
Im still not understanding why though. If i use a 12V battery, it means there will be a total of 12V potential drop around the circuit, right? Let's say i hooked up each terminal of a battery with a resistance free wire. How does this law still apply?
 
  • #7
I do not know a lot of E&M theory as I am a humble EE, but I think if you look at it in terms of Ohm's Law it might make more sense mathematically.

Ohm's Law is I = V/R. Since R = 0 across the resistance-free wire, I = infinity. Thus, voltage across the circuit can mathematically be anything, even 12 V.

Someone else may come along and correct me.
 
  • #8
danago said:
Im still not understanding why though. If i use a 12V battery, it means there will be a total of 12V potential drop around the circuit, right? Let's say i hooked up each terminal of a battery with a resistance free wire. How does this law still apply?
There's no such thing as a resistance free wire (except for a superconductor, but that's another subject).

Let's say you hook up an 18AWG wire across the battery, and the wire's resistance is a few milliOhms. A real battery (as with any real power source) has an internal resistance associated with its particular battery chemistry. So you model the battery as an ideal voltage source (zero output resistance) in series with the battery's output resistance. The short circuit draws a large current from the battery, and the source resistance of the battery limits the short circuit current.

Don't get caught up in the trap of thinking of real world things like batteries and wires in their simplified ideal model terms. Instead, look at real world things and understand how to model them in terms of combinations of ideal elements. That's what you do with SPICE simulations of real circuits, for example.
 

1. What is electrical potential energy?

Electrical potential energy is the energy stored in a system due to the separation of charges. It is a type of potential energy that is related to the position of charged particles in an electric field.

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

Electrical potential energy is a measure of the energy stored in a system, while electrical potential is a measure of the potential energy per unit charge at a specific point in an electric field. In other words, electrical potential energy is a property of a system, while electrical potential is a property of a point in space.

3. What factors affect the electrical potential energy of a system?

The electrical potential energy of a system is affected by the amount of charge present, the distance between the charges, and the strength of the electric field. It is also affected by the type of materials involved, as different materials have different abilities to store electrical potential energy.

4. How is electrical potential energy related to work?

Work is defined as the transfer of energy from one form to another. In the case of electrical potential energy, work is done when charges are moved against an electric field, either to increase or decrease their separation. The amount of work done is equal to the change in electrical potential energy of the system.

5. Can electrical potential energy be converted into other forms of energy?

Yes, electrical potential energy can be converted into other forms of energy, such as kinetic energy or thermal energy. This conversion often occurs when charges are allowed to move freely in an electric circuit, causing them to lose their potential energy and gain other forms of energy.

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