In a battery-powered electric circuit, the cells serve the role of the charge pump to supply energy to the charge to lift it from the low potential position through the cell to the high potential position.
It is often convenient to speak of an electric circuit such as the simple circuit discussed here as having two parts - an internal circuit and an external circuit. The internal circuit is the part of the circuit where energy is being supplied to the charge. For the simple battery-powered circuit that we have been referring to, the portion of the circuit containing the electrochemical cells is the internal circuit. The external circuit is the part of the circuit where charge is moving outside the cells through the wires on its path from the high potential terminal to the low potential terminal.
The movement of charge through the internal circuit requires energy since it is an uphill movement in a direction that is against the electric field. The movement of charge through the external circuit is natural since it is a movement in the direction of the electric field. When at the positive terminal of an electrochemical cell, a positive test charge is at a high electric pressure in the same manner that water at a water park is at a high water pressure after being pumped to the top of a water slide.
Being under high electric pressure, a positive test charge spontaneously and naturally moves through the external circuit to the low pressure, low potential location. As a positive test charge moves through the external circuit, it encounters a variety of types of circuit elements. Each circuit element serves as an energy-transforming device.
Light bulbs, motors, and heating elements such as in toasters and hair dryers are examples of energy-transforming devices. In each of these devices, the electrical potential energy of the charge is transformed into other useful and non-useful forms. For instance, in a light bulb, the electric potential energy of the charge is transformed into light energy a useful form and thermal energy a non-useful form.
The moving charge is doing work upon the light bulb to produce two different forms of energy. By doing so, the moving charge is losing its electric potential energy. Upon leaving the circuit element, the charge is less energized. The location just prior to entering the light bulb or any circuit element is a high electric potential location; and the location just after leaving the light bulb or any circuit element is a low electric potential location.
Referring to the diagram above, locations A and B are high potential locations and locations C and D are low potential locations. The loss in electric potential while passing through a circuit element is often referred to as a voltage drop. By the time that the positive test charge has returned to the negative terminal, it is at 0 volts and is ready to be re-energized and pumped back up to the high voltage, positive terminal.
An electric potential diagram is a convenient tool for representing the electric potential differences between various locations in an electric circuit. Two simple circuits and their corresponding electric potential diagrams are shown below. In Circuit A, there is a 1. In Circuit B, there is a 6-volt battery four 1. In each case, the negative terminal of the battery is the 0 volt location. The positive terminal of the battery has an electric potential that is equal to the voltage rating of the battery.
The battery energizes the charge to pump it from the low voltage terminal to the high voltage terminal. By so doing the battery establishes an electric potential difference across the two ends of the external circuit. Being under electric pressure , the charge will now move through the external circuit. As its electric potential energy is transformed into light energy and heat energy at the light bulb locations, the charge decreases its electric potential.
The total voltage drop across the external circuit equals the battery voltage as the charge moves from the positive terminal back to 0 volts at the negative terminal. In the case of Circuit B, there are two voltage drops in the external circuit, one for each light bulb. While the amount of voltage drop in an individual bulb depends upon various factors to be discussed later , the cumulative amount of drop must equal the 6 volts gained when moving through the battery.
The electrical potential difference across the two inserts of a household electrical outlet varies with the country. Use the Household Voltages widget below to find out the household voltage values for various countries e.
Answer: C. When a force is required to move an electron in the direction of an electric field, its electrical potential energy increases. On the other hand, an electron moving opposite the direction of the electric field will decrease its electrical potential energy.
This is because the electric field direction is in the direction which a positive charge spontaneously moves. An electron is negatively charged. Answer: D. The battery establishes an electric potential difference across the two ends of the external circuit and thus causes the charge to flow. As we will see in a moment, information gleaned from the equipotential map also indicates the relative strength of the magnetic field, which can be used to determine the relative magnitude and direction!
As with the electric field, any configuration of charges has a unique electric potential. That is to say, the potential from a spherical charge, a capacitor, and a charged wire all have unique potentials and fields.
You will have the opportunity to explore several of these during DL. We are asked to span the range of voltages between 10V and 30V with three or four potentials. We know that our equipotentials should be chosen with equal voltage differences, so we chose10V, 20V, and V.
Next, we plot the values, being sure to indicate the scale. Comparing our graph to our expectations, we find they match, so we can proceed to the second part of the problem.
The location is marked with a solid dot. Apparently, the value of the potential is between 20V and 30V, but much closer to 30V. We might estimate a value of 28V. Though it is not asked for in the problem, we can calculate the value of the Bohr potential at that location. Plugging numbers into the formula, we find just over 27V. We now explore the relationship between these quantities.
Using this, we take the derivative with respect to separation distance to find the force between the charges, as we did previously. What does this mean? Refer to the calculus appendix or your favourite introductory calculus book if you need a refresher on calculus.
The electric field is large when the derivative of the electric potential is large. The inverse is also true a fast-changing potential indicates a large field. In the equipotential map representation, a large electric field corresponds to potentials that are close together in those locations, the potential changes rapidly over short distances. Thus, the electric potential energy is dependent upon the amount of charge on the object experiencing the field and upon the location within the field.
Just like gravitational potential energy, electric potential energy is dependent upon at least two types of quantities:.
While electric potential energy has a dependency upon the charge of the object experiencing the electric field, electric potential is purely location dependent.
Electric potential is the potential energy per charge. The concept of electric potential is used to express the effect of an electric field of a source in terms of the location within the electric field. A test charge with twice the quantity of charge would possess twice the potential energy at a given location; yet its electric potential at that location would be the same as any other test charge. A positive test charge would be at a high electric potential when held close to a positive source charge and at a lower electric potential when held further away.
In this sense, electric potential becomes simply a property of the location within an electric field. Suppose that the electric potential at a given location is 12 Joules per coulomb, then that is the electric potential of a 1 coulomb or a 2 coulomb charged object.
Stating that the electric potential at a given location is 12 Joules per coulomb, would mean that a 2 coulomb object would possess 24 Joules of potential energy at that location and a 0. As we begin to discuss electric circuits, we will notice that a battery powered electric circuit has locations of high and low potential.
Charge moving through the wires of the circuit will encounter changes in electric potential as it traverses the circuit. Within the electrochemical cells of the battery, there is an electric field established between the two terminals, directed from the positive terminal towards the negative terminal. As such, the movement of a positive test charge through the cells from the negative terminal to the positive terminal would require work, thus increasing the potential energy of every Coulomb of charge that moves along this path.
This corresponds to a movement of positive charge against the electric field. It is for this reason that the positive terminal is described as the high potential terminal. Similar reasoning would lead one to conclude that the movement of positive charge through the wires from the positive terminal to the negative terminal would occur naturally.
Such a movement of a positive test charge would be in the direction of the electric field and would not require work. The charge would lose potential energy as moves through the external circuit from the positive terminal to the negative terminal.
The negative terminal is described as the low potential terminal. This assignment of high and low potential to the terminals of an electrochemical cell presumes the traditional convention that electric fields are based on the direction of movement of positive test charges. In a certain sense, an electric circuit is nothing more than an energy conversion system. In the electrochemical cells of a battery-powered electric circuit, the chemical energy is used to do work on a positive test charge to move it from the low potential terminal to the high potential terminal.
Chemical energy is transformed into electric potential energy within the internal circuit i. Once at the high potential terminal, a positive test charge will then move through the external circuit and do work upon the light bulb or the motor or the heater coils, transforming its electric potential energy into useful forms for which the circuit was designed.
The positive test charge returns to the negative terminal at a low energy and low potential, ready to repeat the cycle or should we say circuit all over again.
When work is done on a positive test charge to move it from one location to another, potential energy increases and electric potential increases. The following diagrams show an electric field represented by arrows and two points - labeled A and B - located within the electric field.
A positive test charge is shown at point A.
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