20.2 Ohm’s Law: Resistance and Simple Circuits
3 min read•june 18, 2024
Ohm's_Law_0### is the foundation of electrical circuits, linking voltage, current, and resistance. It's like the golden rule of electricity, helping us understand how these three key players interact in everything from simple household wiring to complex electronic devices.
Applying 's Law lets us analyze and design circuits, whether they're series, parallel, or a mix. We can calculate , work with different materials, and use circuit components effectively. It's the starting point for understanding how electricity flows and behaves in our everyday world.
Ohm's Law and Simple Circuits
Voltage, current, and resistance relationships
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- Ohm's law states current () through a directly proportional to voltage () across it and inversely proportional to () mathematically expressed as
- Voltage () measured in volts (V) represents between two points in a circuit drives flow of electric current
- Current () measured in amperes (A) represents flow of electric charge through a depends on applied voltage and conductor resistance
- Resistance () measured in ohms () represents opposition to electric current flow in a conductor depends on material properties and conductor geometry
Applications of Ohm's law
- Given any two of voltage, current, or resistance, the third can be calculated using Ohm's law
- To find voltage:
- To find current:
- To find resistance:
- In series circuits voltage drops across each component add up to total applied voltage, current remains the same through all components, equivalent resistance is sum of individual resistances:
- In parallel circuits voltage remains the same across all components, current divides among parallel branches, reciprocal of equivalent resistance is sum of reciprocals of individual resistances:
- Power in electrical circuits is calculated as , representing the rate at which is transferred or consumed
Ohmic vs non-ohmic materials
- materials obey Ohm's law have constant resistance independent of applied voltage or current (copper, aluminum, silver)
- materials do not obey Ohm's law have resistance that varies with applied voltage or current (semiconductors, diodes, incandescent light bulbs)
Components of simple circuits
- Components
- Voltage sources provide to drive current through circuit (batteries, power supplies)
- Resistors control current flow and provide resistance
- Switches control current flow by opening or closing circuit
- Conductors allow electric current flow with minimal resistance (wires, cables)
-
- (): sum of currents entering a node equals sum of currents leaving the node
- (): sum of voltage drops around any closed loop in a circuit equals zero
- Analyzing circuits
- Identify circuit type: series, parallel, or combination
- Apply Ohm's law and Kirchhoff's laws to determine unknown quantities
- Use equivalent resistance formulas for series and parallel circuits to simplify analysis
Circuit Diagrams and Special Cases
- Circuit diagrams use standardized symbols to represent components and connections in an electrical circuit
- occurs when current bypasses the intended path, often resulting in excessive current flow
- represents a break in the circuit path, preventing current flow
- in circuits is measured in joules (J) and represents the total energy transferred over time
Key Terms to Review (43)
Acceleration: Acceleration is the rate of change of velocity over time. It is a vector quantity, meaning it has both magnitude and direction.
Air resistance: Air resistance is a force that opposes the motion of an object through the air. It depends on the object's speed, surface area, and shape.
Ampere: An ampere (A) is the unit of electric current in the International System of Units (SI). It represents the flow of one coulomb of charge per second.
Ampere: The ampere (symbol: A) is the base unit of electric current in the International System of Units (SI). It is defined as the constant flow of one coulomb of electrical charge per second, and it is a fundamental quantity used to describe the movement of electric charge.
Battery: A battery is a device that stores chemical energy and converts it into electrical energy, providing a source of power for various electrical devices and circuits. It is a fundamental component in the understanding of topics such as electric potential energy, Ohm's law, resistors in series and parallel, and electromotive force.
Circuit Diagram: A circuit diagram is a graphical representation of an electrical circuit that shows the interconnections of its components. It is a fundamental tool used in the study of Ohm's Law and the analysis of simple electrical circuits.
Conductor: A conductor is a material that allows the free flow of electric charge, typically electrons. Conductors are essential in creating electric circuits and are usually made from metals like copper or aluminum.
Conductor: A conductor is a material that allows the free flow of electric charge, enabling the transmission of electrical current. This term is crucial in understanding various topics in physics, including heat transfer methods, electric fields, electric current, and resistance.
Current: Current is the flow of electric charge in a circuit, typically measured in amperes (A). It represents how much charge passes through a point in the circuit per unit of time, and it plays a crucial role in determining how electrical energy is distributed and consumed in various applications.
Electric power: Electric power is the rate at which electrical energy is transferred by an electric circuit. It is typically measured in watts (W).
Electrical energy: Electrical energy is the energy derived from electric potential or kinetic energy of charged particles. It can be converted into various forms such as heat, light, and mechanical energy.
Electrical Energy: Electrical energy is the energy associated with the flow of electric charge, such as the movement of electrons through a conductor. It is the form of energy that powers our electronic devices, lights, and various electrical systems, and is a fundamental concept in the study of physics and electrical engineering.
I: The term 'I' refers to the moment of inertia, a fundamental concept in the study of rotational motion, wave intensity, electrical resistance, and circuit analysis. Moment of inertia describes an object's resistance to changes in its rotational motion, while intensity is a measure of the energy carried by a wave, and resistance is a measure of an object's opposition to the flow of electric current. Understanding the role of 'I' in these various contexts is crucial for comprehending the underlying principles of physics.
KCL: KCL, or Kirchhoff's Current Law, is a fundamental principle in electrical circuits that states the sum of all currents entering and leaving a node (a point where multiple circuit elements connect) must be zero. This law is crucial in understanding the behavior of simple and complex circuits, as it allows for the analysis and prediction of current flow within a circuit.
Kirchhoff's Current Law: Kirchhoff's current law is a fundamental principle in electrical engineering that states the total current flowing into a node or junction must be equal to the total current flowing out of that node. This law is essential for understanding the behavior of electrical circuits and applying Ohm's law to analyze complex networks.
Kirchhoff's Laws: Kirchhoff's Laws are a set of fundamental principles that describe the behavior of electric circuits. They provide a framework for understanding the flow of current and the distribution of voltage in both simple and complex electrical networks.
Kirchhoff's Voltage Law: Kirchhoff's Voltage Law is a fundamental principle in electrical circuits that states the sum of all the voltage drops around a closed loop is equal to zero. It is a crucial concept in understanding the behavior of electrical circuits and applying Ohm's Law.
KVL: KVL, or Kirchhoff's Voltage Law, is a fundamental principle in electrical circuit analysis that states that the algebraic sum of all the voltages around a closed loop in an electrical circuit is zero. It is one of the two Kirchhoff's rules that describe the behavior of current and voltage in a circuit.
Non-Ohmic: Non-ohmic refers to electrical components or 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. Non-ohmic devices exhibit a non-linear relationship between current and voltage, meaning their resistance changes with the applied voltage.
Ohm: An ohm is the unit of electrical resistance in the International System of Units (SI). It represents the resistance between two points of a conductor when a constant potential difference of one volt applied to these points produces a current of one ampere.
Ohm: Ohm is a fundamental unit in electrical engineering that measures the resistance to the flow of electric current in a circuit. It is named after the German physicist Georg Ohm, who discovered the relationship between voltage, current, and resistance in electrical circuits.
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. It is mathematically expressed as $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.
Ohm's Law: Ohm's law is a fundamental principle in electrical engineering that describes the relationship between the voltage, current, and resistance in an electrical circuit. It states that the current flowing through a conductor is directly proportional to the voltage applied across it, and inversely proportional to the resistance of the conductor.
Ohmic: A material or component is considered ohmic if it follows Ohm's Law, where the current through the material is directly proportional to the voltage across it. This relationship is characterized by a constant resistance.
Ohmic: Ohmic refers to a type of electrical behavior where the relationship between voltage and current is linear, following Ohm's law. This means that the resistance of an Ohmic material or device remains constant, regardless of the applied voltage or current.
Open Circuit: An open circuit is an electrical circuit in which the flow of electric current is interrupted, creating a break in the conductive path. This means that the circuit is not complete, and no current can flow through it.
Parallel Circuit: A parallel circuit is an electrical circuit in which components are connected along multiple paths, allowing current to flow through different branches simultaneously. In a parallel circuit, the voltage across each component is the same, while the current through each component can vary.
Potential difference: Potential difference is the work done to move a unit charge between two points in an electric field. It is measured in volts (V) and often referred to as voltage.
Potential Difference: Potential difference, also known as voltage, is the measure of the work required to move 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 behavior of electric circuits and the flow of electric current.
Power: Power is the rate at which work is done or energy is transferred. It is the measure of the amount of energy expended per unit of time. Power is a fundamental concept in physics that is essential for understanding various topics, including work, energy, and simple machines.
R: In physics, 'r' typically represents the distance from a rotation axis or center of mass to a point of interest. This distance is crucial in understanding rotational motion, electric circuits, and how different components interact within a system. It plays a vital role in calculations for rotational inertia, resistance, and electromotive force, linking the concepts of linear and angular relationships in physics.
Resistance: Resistance is a measure of the opposition to the flow of electric current in a material. It is measured in ohms ($\Omega$).
Resistance: Resistance is a measure of the opposition to the flow of electric current in a circuit. It is a fundamental concept in electrical engineering and physics, as it determines the behavior of electrical systems and the energy dissipation within them.
Resistor: A resistor is an electrical component that limits or regulates the flow of electrical current in a circuit. It provides resistance, measured in ohms ($\Omega$), to control voltage and current levels.
Resistor: A resistor is a passive electronic component that is used to control or limit the flow of electric current in a circuit. It is a fundamental element in electrical and electronic systems, playing a crucial role in various applications such as voltage division, current regulation, and signal processing.
Series Circuit: A series circuit is an electrical circuit in which the components are connected end-to-end, forming a single continuous path for the flow of electric current. This arrangement ensures that the same current flows through each component in the circuit.
Short Circuit: A short circuit is an abnormal, low-resistance connection between two points in an electrical circuit, which allows a large amount of current to flow and potentially cause damage or a fire. This term is particularly relevant in the context of Ohm's Law and simple electrical circuits.
Simple circuit: A simple circuit consists of a power source, a conductive path, and a load. It allows electric current to flow through a closed loop.
Switch: A switch is an electrical component that is used to control the flow of electric current in a circuit. It acts as a gateway, allowing or interrupting the passage of electricity based on the user's input or a predetermined condition.
V: In physics, 'v' represents velocity, which is a vector quantity that indicates the rate of change of an object's position with respect to time, including its direction. Velocity is crucial in understanding motion, as it not only tells how fast an object is moving but also in which direction it is traveling. This concept extends beyond simple motion to fluid dynamics and electrical circuits, highlighting its versatility across different scientific fields.
Volt: A volt is the unit of electric potential difference, which measures the amount of electric potential energy per unit charge between two points in an electric circuit. It helps us understand how much energy is available to move electric charges through a conductor, connecting it to concepts like power, energy storage, and circuit behavior.
Voltage: Voltage, also known as potential difference, is the electrical potential energy difference between two points in an electrical circuit. It is the driving force that causes the flow of electric current, and it is measured in units of volts (V).
Voltage Source: A voltage source is a device that maintains a constant potential difference, or voltage, between two points in an electrical circuit. It is the driving force that pushes electric charge through the circuit, providing the energy necessary for the circuit to function.