9.4 Ohm's Law
2 min read•june 24, 2024
's law is the backbone of electrical circuit analysis, linking , , and . It's crucial for understanding how electricity flows and how components interact in circuits. Knowing this law helps predict circuit behavior and troubleshoot issues.
Ohm's law calculations are essential for designing and analyzing circuits. By mastering these calculations, you can determine unknown values, analyze consumption, and understand the differences between and in various electrical applications.
Ohm's Law
Ohm's law fundamentals
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- Ohm's law describes the relationship between voltage (), current (), and resistance () in an electrical circuit
- Current is directly proportional to voltage and inversely proportional to resistance
- [V = IR](https://www.fiveableKeyTerm:V_=_IR) is the mathematical expression of Ohm's law
- Voltage measured in (V)
- Current measured in (A)
- Resistance measured in ()
- Doubling the voltage across a with constant resistance doubles the current flowing through it (proportional increase)
- Doubling the resistance of a with constant voltage halves the current flowing through it (proportional decrease)
- The electric field within a conductor drives the movement of , resulting in current flow
Ohm's law calculations
- Ohm's law used to calculate voltage, current, or resistance when the other two quantities are known
- Voltage calculation:
- Current calculation:
- Resistance calculation:
- Identify the specific portion of the circuit being analyzed and the direction of current flow before applying Ohm's law
- Series circuits have the same current through all components, and the total voltage is the sum of the individual component voltages (voltage divider)
- Parallel circuits have the same voltage across all components, and the total current is the sum of the individual component currents ()
Ohmic vs nonohmic materials
- exhibit a linear current-voltage relationship with constant resistance regardless of applied voltage
- Most metals are ohmic (copper, aluminum)
- Current-voltage graph for ohmic materials is a straight line with a slope equal to
- Nonohmic materials have a nonlinear current-voltage relationship, and their resistance changes with applied voltage
- (, ), some liquids, and gases are nonohmic
- Current-voltage graph for nonohmic materials is not a straight line, and the slope (resistance) varies with applied voltage
- Ohm's law is only valid for ohmic materials due to the requirement of constant resistance for the linear voltage-current relationship
- The of a material influences its adherence to Ohm's law
Power and Electric Potential Difference
- Power in electrical circuits is the rate at which energy is transferred or converted
- (voltage) is the work done per unit charge to move a charge between two points in an electric field
- Power can be calculated using Ohm's law:
Key Terms to Review (29)
Ac current: AC current, or alternating current, is an electric current that reverses direction periodically. It is commonly used in power supply systems due to its efficient transmission over long distances.
Ac voltage: AC voltage is a type of electrical current where the voltage periodically changes direction. It is commonly used in household power supplies and electrical grids due to its efficiency in long-distance transmission.
Amperes: Amperes, often abbreviated as 'amps,' are the unit of electric current in the International System of Units (SI). This measure indicates the amount of charge that flows through a conductor over a specific period of time. Understanding amperes is essential for analyzing electrical circuits, as they directly relate to the flow of electrons and interact with voltage and resistance in Ohm's Law, illustrating how current behaves under different conditions.
Charge Carriers: Charge carriers are the mobile, electrically charged particles that are responsible for the flow of electric current in a material. They are the fundamental components that enable the conduction of electricity and are central to understanding various electrical phenomena.
Conductivity: Conductivity is a measure of a material's ability to allow the flow of electric charge or current through it. It is an important property that determines how effectively a substance can conduct electricity and is a crucial factor in understanding various electrical phenomena.
Conductor: A conductor is a material that allows the free flow of electric charge, typically electrons. Metals like copper and aluminum are common examples of conductors.
Conductor: A conductor is a material that allows the free flow of electric charge, enabling the efficient transfer of electrical current. This property is crucial in various topics within physics, including conductors, insulators, and charging by induction, as well as in understanding equipotential surfaces, Ohm's Law, and motional electromotive force (EMF).
Current: Current is the rate of flow of electric charge through a given area, typically measured in amperes (A). It is a fundamental concept in the study of electricity and electromagnetism, as it describes the movement of electric charges and is essential for understanding various electrical phenomena.
Current Divider: A current divider is a circuit configuration that allows the division of an input current into two or more paths, with the current in each path being proportional to the resistance in that path. It is a fundamental concept in understanding the behavior of resistors connected in parallel.
Diode: A diode is a semiconductor device that allows current to flow in one direction only, providing low resistance in one direction and high resistance in the opposite. It is commonly used for rectification, converting AC to DC.
Diodes: A diode is a semiconductor device that allows electric current to flow in only one direction, acting as a one-way valve for electrons. Diodes are fundamental components in electronic circuits, used for various applications such as rectification, signal modulation, and voltage regulation.
Electric Potential Difference: Electric potential difference, also known as voltage, is the work done per unit charge in moving an electric charge between two points in an electric field. It represents the difference in electric potential energy between two locations and is a fundamental concept in understanding the flow of electric current.
Electrical conductivity: Electrical conductivity is a measure of a material's ability to conduct an electric current. It is the reciprocal of electrical resistivity and is denoted by the symbol $\sigma$.
Equivalent resistance: Equivalent resistance is the total resistance of a combination of resistors connected either in series or parallel. It simplifies complex circuits into a single resistor value that has the same effect on the circuit.
Nonohmic Materials: Nonohmic materials are electrical materials that do not follow Ohm's law, which states that the current through a conductor is directly proportional to the voltage applied across it. These materials exhibit a nonlinear relationship between current and voltage, making them behave differently than traditional ohmic materials.
Ohm: An ohm is the unit of electrical resistance in the International System of Units (SI). It is symbolized by the Greek letter omega (Ω).
Ohm’s law: Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them. Mathematically, it is represented as $I = \frac{V}{R}$ where $I$ is current, $V$ is voltage, and $R$ is resistance.
Ohmic: A material is considered ohmic if it follows Ohm's Law, meaning its resistance remains constant regardless of the voltage applied. The current through an ohmic material is directly proportional to the voltage across it.
Ohmic Materials: Ohmic materials are a class of electrical conductors that exhibit a linear relationship between the applied voltage and the resulting current, as described by Ohm's Law. These materials maintain a constant resistance, regardless of the voltage or current applied, making them essential in various electrical and electronic applications.
Ohms: Ohms is a unit of electrical resistance, named after the German physicist Georg Ohm. It represents the resistance in an electrical circuit that limits the flow of electric current, as described by Ohm's Law.
Power: Power is the rate at which energy is transferred or the rate at which work is done. It is a fundamental concept in physics that describes the ability to perform work or cause change over time. Power is a crucial factor in understanding and analyzing various physical phenomena, including electrical circuits, mechanical systems, and energy conversion processes.
Resistance: Resistance is a measure of the opposition to the flow of electric current in an electrical circuit. It is a fundamental concept in understanding the behavior of electric circuits and the relationship between voltage, current, and power.
RLC series circuit: An RLC series circuit is an electrical circuit consisting of a resistor (R), an inductor (L), and a capacitor (C) connected in series with an AC power source. This type of circuit can exhibit resonance, where the inductive and capacitive reactances cancel each other out.
Semiconductors: Semiconductors are materials that have electrical conductivity between that of conductors, such as metals, and insulators, such as ceramics. They are the foundation of modern electronics, enabling the development of devices like transistors, integrated circuits, and microprocessors.
Series Circuit: A series circuit is an electrical circuit in which the components are connected end-to-end in a single loop, allowing only one path for the current to flow. The current is the same through each component in a series circuit.
Transistors: A transistor is a semiconductor device that regulates current or voltage flow. It acts as an amplifier and a switch, and is the fundamental building block of modern electronic devices and circuits, including those used in Ohm's Law.
V = IR: V = IR, also known as Ohm's Law, is a fundamental relationship in electrical circuits that describes the relationship between voltage (V), current (I), and resistance (R). It states that the voltage across a resistor is directly proportional to the current flowing through it, and the constant of proportionality is the resistance of the resistor.
Voltage: Voltage, also known as electrical potential difference, is the driving force that causes the flow of electric current in a circuit. It is the measure of the potential energy difference between two points in an electrical system, and it is the key factor that determines the rate at which electric charge moves through a conductor.
Volts: Volts, often denoted by the symbol 'V', are the units used to measure the electrical potential difference or voltage in an electrical circuit. Voltage is the driving force that pushes electric charge, such as electrons, through a conductor, like a wire, and is a fundamental concept in the study of Ohm's Law.