Unit of Electric Current
Electric current is the flow of electric charge through a material. It is the rate at which electric charge flows past a point in a circuit. The flow of electric charge is typically carried by electrons, which are negatively charged particles.
The SI unit for current is the coulomb per second, or the ampere (A), which is an SI base unit:
1 ampere = 1A = 1 coulomb per second = 1 C/s.
The ampere (A) is defined as the rate at which electric charge flows through a surface per unit of time. One ampere is equal to a flow of one coulomb of electric charge per second.
The ampere is one of the seven base units in the International System of Units (SI) and is used to measure electric current in all practical applications. It is named after the French physicist André-Marie Ampère, who was one of the founders of the study of electromagnetism.
Examples of Electric Currents in Amperes
Here are ten examples of electric currents in amperes, sorted from smallest to largest:
- The current required to light up an LED (Light Emitting Diode) is typically between 10-20 milliamperes (mA).
- The charging current of a small USB-powered device, such as a smartphone, is typically around 1 ampere (A).
- The current flowing through a household light bulb when it is turned on is typically between 0.1 and 1 A.
- The current flowing through a typical laptop charger is around 2-3 A.
- The current required to start a car engine is typically around 50-100 A.
- The current flowing through a household electric stove when all of its heating elements are turned on can range from 20 to 50 A.
- The current flowing through a high-speed train can range from 1,000 to 3,000 A.
- The current flowing through a typical electric car charging station can range from 20 to 400 A, depending on the charging rate.
- The current required to power a small electric motor, such as the ones used in power tools or household appliances, can range from a few amperes to several hundred amperes.
- The current flowing through a typical industrial welding machine can range from 50 to 500 A.
Electric Current and Hydraulic Analogy
The hydraulic analogy, or the electric-fluid analogy, is a widely used analogy between hydraulics and electricity, which is a useful tool for teaching and for those who are struggling to understand how circuits work. it can also be applied to heat transfer problems.
Current is equivalent to a hydraulic volume flow rate; that is, the volumetric quantity of flowing water over time. Usually measured in amperes. The wider pipe is, the more water will flow through. It is measured in amps (I or A).
Resistance is like pipe diameter or obstacles in the hose that slow down the water flow. It is measured in ohms (Ω). In hydraulics, resistance is associated with the pressure loss coefficient.