Undergraduate
  1. Classical mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. projectile motion  1.1.4. Relative speed  1.1.5. Uniform circular motion  1.1.6. Non-uniform circular motion  1.1.7. Reference frames and transformations  1.2. Newton's Laws of Motion  1.2.1. First law of motion  1.2.2. Second law of motion  1.2.3. Third Law of Motion  1.2.4. Applications of Newton's Laws  1.2.5. Friction and its types  1.2.6. Free Body Diagram  1.2.7. Constraints and pseudo-forces  1.3. Work and Energy  1.3.1. work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy in classical mechanics  1.3.5. Conservative and non-conservative forces  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.4. Speed and collisions  1.4.1. Linear momentum  1.4.2. Conservation of momentum  1.4.3. Impulse and impact force  1.4.4. Elastic and inelastic collision  1.4.5. Center of mass and speed  1.4.6. Rocket Propulsion  1.5. Rotational motion  1.5.1. Torque and Angular Momentum  1.5.2. Moment of inertia  1.5.3. Rotational Kinematics  1.5.4. Rotational Energy  1.5.5. Rolling Motion  1.5.6. Precession and gyroscopic motion  1.6. Gravitational force  1.6.1. Newton's law of universal gravitation  1.6.2. Gravitational potential energy  1.6.3. Orbital mechanics  1.6.4. Kepler's laws of planetary motion  1.6.5. Gravitational field and potential  1.7. Fluid mechanics  1.7.1. Pressure and Pascal's Principle  1.7.2. Buoyancy and Archimedes' principle  1.7.3. Fluid Dynamics and Bernoulli's Principle  1.7.4. Viscosity and Poiseuille's law  1.7.5. Surface tension and capillarity  1.8. Oscillations and waves  1.8.1. Simple Harmonic Motion  1.8.2. Damped and driven oscillations  1.8.3. Coupled oscillations and common modes  1.8.4. Wave properties and types  1.8.5. Sound Waves and the Doppler Effect  1.8.6. Wave interference and superposition
  2. Electromagnetism  2.1. Electrostatics  2.1.1. Electric charge and properties  2.1.2. Coulomb's law  2.1.3. Electric field and electric potential  2.1.4. Gauss's Law  2.1.5. Capacitance and Dielectric  2.1.6. Electric dipole and potential energy  2.2. Electric circuits  2.2.1. Current and Resistance  2.2.2. Ohm's law  2.2.3. Kirchhoff's Laws  2.2.4. RC Circuit  2.2.5. AC Circuits and Reactance  2.2.6. Electric power and energy  2.3. Magnetism  2.3.1. Magnetic Fields and Forces  2.3.2. Ampere's Law  2.3.3. Magnetic dipole moment  2.3.4. Biot-Savart law  2.3.5. Magnetic Materials and Hysteresis  2.4. Electromagnetic induction  2.4.1. Faraday's Law  2.4.2. Lenz's law  2.4.3. Self and mutual induction  2.4.4. Transformers and Inductive Circuits  2.5. Maxwell's equations  2.5.1. Gauss's law for electricity  2.5.2. Gauss's law for magnetism  2.5.3. Faraday's law of induction  2.5.4. Ampere-Maxwell law  2.5.5. Electromagnetic waves
  3. Thermodynamics  3.1. Laws of Thermodynamics  3.1.1. Zeroth law of thermodynamics  3.1.2. First law of thermodynamics  3.1.3. Second Law  3.1.4. Third Law  3.2. Heat and work  3.2.1. Heat transfer (conduction, convection, radiation)  3.2.2. Thermal expansion  3.2.3. Heat engines and refrigerators  3.2.4. Carnot cycle and efficiency  3.3. Statistical mechanics  3.3.1. Maxwell–Boltzmann distribution  3.3.2. Entropy and Probability  3.3.3. Partition function  3.3.4. Fermi–Dirac and Bose–Einstein statistics
  4. Optics  4.1. Geometrical Optics  4.1.1. Reflection and Refraction  4.1.2. Mirrors and lenses  4.1.3. Optical Instruments  4.1.4. Fermat's principle  4.2. Wave optics  4.2.1. Interference in wave optics  4.2.2. Diffraction  4.2.3. Polarization  4.2.4. Coherence and holography
  5. Quantum mechanics  5.1. Wave–particle duality  5.1.1. Blackbody radiation in wave–particle duality in quantum mechanics  5.1.2. Photoelectric effect  5.1.3. Compton scattering  5.1.4. De Broglie wavelength  5.2. Schrödinger Equation  5.2.1. Time-independent Schrödinger equation  5.2.2. Particle in a box  5.2.3. Quantum Tunneling  5.2.4. Potential wells and obstacles  5.3. Quantum States  5.3.1. Wave function  5.3.2. Quantum operators  5.3.3. Heisenberg uncertainty principle  5.3.4. Angular momentum and spin
  6. Relativity  6.1. Special relativity  6.1.1. Lorentz transformations  6.1.2. Time expansion and length contraction  6.1.3. Relativistic energy and momentum  6.2. General relativity  6.2.1. Principle of Equivalence  6.2.2. Schwarzschild metric  6.2.3. Gravitational waves  6.2.4. Black holes and event horizons
  7. Solid state physics  7.1. Crystal structure  7.1.1. Bravais lattices  7.1.2. X-ray diffraction  7.1.3. Band theory  7.1.4. Phonons and lattice vibrations  7.2. Electrical and Magnetic Properties  7.2.1. Conductors, Semiconductors and Insulators  7.2.2. Superconductivity  7.2.3. Hall effect
  8. Nuclear and particle physics  8.1. Atomic Structure  8.1.1. Atomic Model  8.1.2. Nuclear binding energy  8.2. Radioactivity  8.2.1. Alpha, beta, gamma decay  8.2.2. Half life  8.2.3. Nuclear Fission and Fusion  8.3. Particle physics  8.3.1. Standard Model  8.3.2. Quarks and Leptons  8.3.3. antimatter  8.3.4. Fundamental interactions
  9. Astrophysics and cosmology  9.1. Stellar evolution  9.1.1. Star formation  9.1.2. Black holes and neutron stars  9.1.3. White dwarfs and supernovae  9.2. Cosmology  9.2.1. The Big Bang Theory  9.2.2. Dark matter and dark energy  9.2.3. Cosmic microwave background

Undergraduate → Electromagnetism → Electric circuits ↓


Ohm's law


Ohm's law is one of the fundamental principles for understanding electrical circuits. It relates voltage, current, and resistance in a circuit and is essential for analyzing the operation of circuits. The law is named after the German physicist Georg Simon Ohm, who first formulated it. His work has laid the groundwork for modern circuit design and electrical engineering.

Basics of electrical circuit

Before understanding Ohm's law, it is important to have a basic understanding of electrical circuits. An electrical circuit is a path that allows the flow of electricity, consisting of various electrical components such as resistors, capacitors and power sources. The basic components of electrical circuits are:

  • Voltage (V): This is the electric potential difference between two points in a circuit. Voltage is what drives electric current through a circuit. It is measured in volts (V).
  • Current (I): It is the flow of electric charge in a circuit. Current is measured in amperes (A).
  • Resistance (R): It is the opposition to the flow of current in a circuit. Resistance is measured in ohms (Ω).

Ohm's law: relationship between voltage, current and resistance

Ohm's law provides a simple formula that combines these three fundamental properties in circuits. This law is expressed as follows:

V = I * R

Where V is the voltage in volts, I is the current in amperes, and R is the resistance in ohms. This formula tells us that the voltage across a conductor is equal to the current flowing through it plus its resistance. This simple relationship can be rearranged as follows:

I = V / R
R = V / I

These rearrangements help us understand how a change in one quantity affects other quantities. Ohm's law is fundamental to understanding electrical circuits and their functioning.

Visual example

Let's consider a simple circuit consisting of a battery, a resistor, and a connecting wire. You can visualize a simple circuit using the following representation:

<--|Battery|----(Resistor)------>
<--|Battery|----(Resistor)------>
Battery --> Current Flow Obstructions

In this example, the battery provides voltage, the resistor opposes the current, and current flows through the resistor from the positive terminal of the battery to the negative terminal.

Lesson example using Ohm's law

Example 1: Determination of current

Suppose you have a circuit with a resistance of 5 ohms and a voltage of 10 volts. To find the current flowing in the circuit, you can use Ohm's law:

I = V / R

Substituting the values, you will get:

I = 10V / 5Ω = 2A

The current flowing in the circuit is 2 amperes.

Example 2: Calculating resistance

In another scenario, imagine that you know the voltage in a circuit is 20 volts and the current flowing through it is 4 amperes. To find the resistance, rearrange Ohm's law as follows:

R = V / I

Substituting the values, you will get:

R = 20V / 4A = 5Ω

The resistance in the circuit is 5 ohms.

Example 3: Finding voltage

Consider a circuit with a resistance of 8 ohms and a current of 3 amperes. To find the voltage, use Ohm's law:

V = I * R

Substituting the values, you will get:

V = 3A * 8Ω = 24V

The voltage across the circuit is 24 volts.

Applications of Ohm's law

Ohm's law is important in practical applications, especially in the design and analysis of electrical circuits. Some major applications include:

  • Electrical distribution: Engineers use Ohm's law to ensure that electrical systems are able to carry the required current without overheating or causing damage.
  • Electronic devices: Designers calculate the proper resistance needed for components of devices such as mobile phones, computers and televisions to function safely and efficiently.
  • Power consumption: Understanding the relationships between voltage, current, and resistance helps design systems that reduce energy waste and increase efficiency.
  • Safety measures: Ohm's law can help design circuits that prevent overloads and short circuits, reducing the risk of fire or property damage.

Limitations and considerations

Although Ohm's law is widely applicable, there are limitations to its use. Ohm's law assumes that resistance remains constant over a range of voltages and currents, which may not be true for all materials. For example:

  • Non-ohmic materials: Some materials, such as semiconductors or components such as diodes, do not have constant resistance, so they do not obey Ohm's law in all situations.
  • Changes in temperature: Resistance in some materials can change with temperature, affecting the direct application of Ohm's law.

Conclusion

Understanding Ohm's Law is fundamental for anyone studying or working with electric circuits. Its simplicity as a formula provides profound insight into how electrical components interact, allowing for the effective design and troubleshooting of electrical systems. Despite its simplicity, correct application of Ohm's Law requires consideration of the nature of materials and the conditions under which they operate.

Further exploration

To learn more about Ohm's Law, consider doing practical experiments with different resistors and measuring voltage, current, and resistance to see the relationships directly. Lab kits and electronic test equipment can help provide a more thorough understanding of these fundamental concepts.


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Ohm's law

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