Beatrice Lang
Electric potential, often referred to as voltage, is a fundamental concept in understanding how electric circuits function. It refers to the potential difference between two points in a circuit, and it plays a crucial role in determining how electrical energy is converted and distributed within the circuit. The electric potential is highest at the positive terminal of a battery, and it decreases as a unit charge moves away from this point. This is because the positive terminal is at a higher voltage than the negative terminal, and the potential difference is essentially the change in potential energy of a charge as it moves between these two points. So, where exactly is the electric potential greatest within a circuit, and how does this impact the overall behaviour of the circuit?
| Characteristics | Values |
|---|---|
| Electric potential | Greatest at the positive terminal of a battery |
| Electric potential difference | Depends on the work done by the electric force |
| Voltage | Potential difference between two points in a circuit |
| Current | Maintained by electric potential, no resistance means no potential needed |
| Electric field | Allows calculation of force on a charge, direction depends on charge type |
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What You'll Learn
Electric potential and potential difference
Electric potential, also referred to as voltage drop, is the work done per unit charge to bring that charge from infinity to a point in an electrostatic field against the field force. The SI unit for electric potential is volts or voltage. Electric potential is a scalar quantity.
Electric potential difference, also known as voltage, is the work done per unit charge to move a unit charge from one point to another in an electric field. The SI unit of electric potential difference is the same as electric potential, i.e., voltage or volts. A voltmeter is used to measure the electric potential difference, which is applied in parallel to the instrument whose voltage is to be measured.
The electric potential difference is required to create the flow of electrons and produce electricity. The current always moves from higher potential to lower potential. The longer side represents the higher potential (+ve terminal), and the shorter side represents the lower potential (-ve terminal).
The relationship between potential difference (or voltage) and electrical potential energy is given by the formula: Voltage = Energy/Unit Charge. Thus, two batteries can have the same voltage but differ in the amount of energy they store. For example, a motorcycle battery and a car battery can both have the same voltage, but the car battery can move more charge and store more energy.
The potential difference is also related to the energy gained by charged particles accelerated through it. An electron accelerated through a potential difference of 1 volt gains 1 electron-volt (eV) of energy. Similarly, an ion with a double positive charge accelerated through 100 volts gains 200 eV of energy.
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Voltage
In a basic circuit with a battery and a resistor, the electric potential at a point before the resistor (Point C) can be equal to the electromotive force (emf) of the battery. The emf represents the work done per unit charge to move a positive charge from the negative terminal to the positive terminal of the battery. As the positive terminal has a higher electric potential energy, moving a positive charge away from this terminal towards a more distant point through a conducting wire results in a decrease in electric potential.
The electric potential at Point C, just before the resistor, is higher compared to Point D, which is located after the resistor. When a charge reaches the resistor, it encounters a higher potential at one end (usually the left end) and a lower potential at the other end. This potential difference creates an electric force that causes the charge to flow through the resistor.
It is important to distinguish between potential difference and electrical potential energy. Voltage, or potential difference, represents the energy per unit charge. Therefore, two batteries can have the same voltage but differ in the total amount of energy they store. Voltage helps us understand how to maintain a constant current in a circuit. In the absence of resistance, there is no potential difference, and zero potential is required to sustain the current.
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Electric potential energy
In a circuit, the difference in electric potential energy between two points is often referred to as voltage. Voltage, or potential difference, represents the energy per unit charge. It is important to distinguish between potential difference and electrical potential energy. While voltage quantifies the energy per unit charge, electrical potential energy depends on the position of the charged particle within the electric field.
The electric potential energy of a charged particle is influenced by its movement within the electric field. When a charged particle moves from a point of higher potential energy to a point of lower potential energy, the force does positive work, and the potential energy decreases. Conversely, when the charged particle moves against the electric force, from a point of lower potential energy to a point of higher potential energy, the force does negative work, and the potential energy increases.
In the context of a battery, the positive terminal is considered the terminal of high potential energy. This is because a unit charge at this point possesses high electric potential energy. As the unit charge moves away from the positive terminal through a conducting wire, the electric potential energy decreases. The battery provides an electromotive force (emf), which is the electrical energy per unit charge required to drive a unit charge through a closed circuit. The emf is equivalent to the work done by the electric field.
It is worth noting that in a circuit with conducting wires, a battery, and a resistor, the electric potential at the point before the resistor (Point C) is influenced by the emf of the battery. If the wire before the resistor is an equipotential surface, the charges can move freely without any forces acting on them, resulting in no change in energy. However, when the charge encounters the resistor, it experiences a force due to the potential difference between the two ends of the resistor. This force results in a change in potential energy as the charge moves through the circuit.
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$23.34
Electric field
In a circuit with a battery and a resistor, the electric field exerts a force on the electrons, causing them to move from the negative terminal of the battery through the circuit to the positive terminal. This movement of electrons creates an electric current. The electric potential, or voltage, between two points in a circuit is the energy per unit charge. It represents the work done by the electric field to move a unit charge between these points.
The electric potential is greatest at the positive terminal of the battery, also known as the terminal of high potential. This is because a unit charge at this point possesses high electric potential energy. As the unit charge moves away from the positive terminal through a conducting wire, the electric potential decreases. This decrease in electric potential energy translates to a negative electric potential difference between two points, A and B, where A is closer to the positive terminal and B is further away.
The presence of a resistor in the circuit introduces an interesting dynamic. Before the resistor, the wire can be considered an equipotential surface, where charges can move freely without any forces acting on them. However, when the charges encounter the resistor, they experience a force due to the difference in potential between the two ends of the resistor. This force propels the charges through the resistor, converting electrical energy into other forms of energy, such as light or mechanical work.
The electric field's ability to do work on charges is analogous to gravitational potential energy. Just as an object's gravitational potential energy depends on its height above the Earth's surface, the electric potential energy of a charged particle depends on its position within the electric field. Understanding these concepts is crucial for designing and analysing electric circuits, ensuring efficient energy conversion and utilisation.
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Electromotive force
EMF is produced by either an electrochemical cell or by changing the magnetic field. In batteries, chemical reactions at the electrode-electrolyte interfaces drive the current. The ""seat of the electromotive force"" was determined by Walther Nernst in 1889 to be primarily at these interfaces. The EMF produced by primary (single-use) and secondary (rechargeable) cells is usually a few volts, but it can vary depending on the load and the state of the cell.
Electrical transducers are devices that provide EMF by converting other forms of energy into electrical energy. For example, batteries convert chemical energy, while generators convert mechanical energy. This energy conversion is achieved by physical forces applying work to electric charges.
EMF can be induced in a coil or conductor when there is a change in flux linkages. There are two types of EMF induction: static and dynamic. Static induction occurs when a conductor is moved in a stationary magnetic field, resulting in a change in flux linkage. Dynamic induction happens when the change in flux linkage arises from a change in the magnetic field around a stationary conductor.
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Frequently asked questions
The electric potential is greatest at the positive terminal of the battery. The positive terminal is at a higher voltage than the negative terminal.
The difference in electric potential between two points in a circuit is called the voltage. Voltage is the potential difference between two points, measured in joules per coulomb (V).
Electric potential is related to the work done by the electric field and the energy associated with electrical interactions. The work done by the electric field is equal to the electrical energy per unit charge. Electric potential energy depends on the position of charged particles in the electric field.
