Ohm’s law is the relationship between electrical conductors and their resistance, which establishes that the current that passes through the conductors is proportional to the voltage applied to them .
The German physicist Georg Simon Ohm (1787-1854) was the first to experimentally demonstrate this relationship.
Ohm’s Law Statement
Ohm discovered in the early 1800s that the current through a metal was directly proportional to the voltage or electrical potential difference by the metal. Ohm’s discovery led to the idea of resistance in circuits.
Ohm’s law expressed as an equation is V = RI, where V is the electrical potential in volts, I is the current in amps, and R is the resistance in ohms.
Ohm triangle, where the relationships between voltage, current and resistance are observed.
To understand Ohm’s law, we need to clarify the concepts of charge, current, and voltage.
Key concepts of Ohm’s law
Load
The source of all electrical charges resides in the atomic structure . The charge of an electron is the basic unit of charge. The measure for the charge is the coulomb (C) in honor of the French physicist Charles Augustin de Coulomb. The charge of an electron is equal to 1.60 x10 -19 C. This means that a charge of 1 C is equal to the charge of 6.25×10 18 electrons.
Conductors
Those substances where charges move easily are called conductors . Metals are excellent conductors due to the displacement or movement of their electrons in their atomic crystal structure.
For example, copper, which is commonly used in cables and other electrical devices, contains eleven valence electrons. Its crystalline structure consists of twelve copper atoms linked through its misplaced electrons. These electrons can be considered as a sea of electrons with the ability to migrate through the metal.
Ohmic conductors
Ohmic conductors are those that comply with Ohm’s law, that is, the resistance is constant at constant temperature and does not depend on the applied potential difference. Example: metallic conductors.
Non-ohmic conductors
They are those conductors that do not follow Ohm’s law, that is, the resistance varies depending on the applied potential difference. Example: certain components of electronic devices such as computers, cell phones, etc.
Insulators
Instead, those substances that resist the movement of the load are called insulators. The valence electrons in insulators, such as water and wood, are strongly restricted and cannot move freely through the substance.
Electric cables are a good example of conductor and insulator: the metal inside conducts electricity while the plastic sheath is insulating.
Stream
Electric current is the flow of charge through a conductor per unit of time . The electric current is measured in amps (A). An ampere is equal to the flow of 1 coulomb per second, that is, 1A = 1C / s.
Voltage
The electric current flowing through a conductor depends on the electrical potential or voltage and the resistance of the conductor to the load flow.
Electric current is comparable to the flow of water. The difference in water pressure in a hose allows water to flow from high pressure to low pressure. The electrical potential difference measured in volts allows the flow of electrical charges through a cable from a high to a low potential zone.
The water pressure is maintained by a pump, and the potential difference for the charge is maintained by a battery.
Electric resistance
Electrical resistance is the difficulty with which electrical charges flow through a conductor.
Using the analogy of water, electrical resistance can be compared to the friction of water flow through a tube. A smooth and polished tube offers little resistance to the passage of water, while a rough and full tube of waste will make the water move more slowly.
Electrical resistance is related to the interaction of the conducting electrons as they move from atom to atom through the conductor. Resistance is measured in ohms or ohms, and is represented by the Greek letter omega Ω.
Key points to remember
- Voltage moves current while resistance prevents it.
- Ohm’s law refers to the relationship between voltage and current.
- Circuits or components that obey the relation V = IR are known as ohmic and present current-voltage graphs that are linear and pass through the zero point.
- A mnemonic to remember the formula Ohm is to remember that Victoria is the R eina of I nglaterra; V = RI
