# What is Current and Voltage in Electronics

Current and Voltage in Electronics

In electrical circuits, it is important to keep track of two quantities: voltage and current. Both voltage and current usually change with time.

What is Voltage (symbol: V, or sometimes E)

The cost in energy (work done) necessary to shift a unit of positive charge from a more negative position (lower potential) to a more positive location is the voltage between two places (higher potential). It is, in other words, the energy released as a unit charge goes "downhill" from a higher to a lower potential. The potential difference or electromotive force (EMF)  is also referred to as voltage (EMF). The volt is the standard unit of measurement, with voltages given in volts (V), kilovolts (1kV = 103V), millivolts (1mV = 10-3V), and microvolts (1µV = 10-6 V). To transport a coulomb of charge over a potential difference of one volt, a joule of effort is required. (A coulomb is a unit of electric charge that roughly matches the charge of 6 x 1018 electrons).  The uncommonly used other voltage levels are nanovolts (1nV = 10-9 V) and megavolts (1MV = 106 V).

What is Current (symbol: I )

Current is the rate of flow of electric charge past a point. The unit of measure is the ampere, or amp, with currents usually expressed in amperes (A), milliamperes (1mA = 10-3A), microamperes (1µA = 10-6A), nano-amperes (1nA = 10-9A), or occasionally picoamperes (1pA = 10-12A). A current of one ampere equals a flow of one coulomb of charge per second. By convention, current in a circuit is considered to flow from a more positive point to a more negative point, even though the actual electron flow is in the opposite direction.

The rate of flow of electric charge through a location is known as current. Currents are commonly represented in amperes (A),

milliamperes (1mA = 10-3A),

microamperes (1µA= 10-6A)

nano-amperes (1nA = 10-9A), or

picoamperes (1pA = 10-12A) as the unit of measurement.

A current of one ampere corresponds to a charge flow of one coulomb per second. Even though the real electron movement is in the opposite drection, the current in a circuit is assumed to flow from a more positive point to a more negative point.

Note: Usually voltage in a circuit is referred to as voltage between two points or voltage across two points. Always use the term "current" to describe the flow of electricity through a device or circuit connection.

It's incorrect, or worse, to state anything like "the voltage across a resistor..." We do, however, commonly refer to the voltage at a circuit's point. This is always taken to indicate the voltage between that point and "ground," which appears to be a well-known position in the circuit.

Voltages are formed by working with charges in devices like batteries (electrochemical), generators (magnetic forces), solar cells (photovoltaic conversion of photon energy), and so on. We get currents by connecting elements (active and passive) with voltages.

The oscilloscope is the most valuable electronic tool because it allows one to look at voltages (and sometimes currents) in a circuit as a function of time. it is often termed as the "eye" of an electronic engineer.

Wires, metallic conductors, and the identical voltage on each of them are used to link items in actual circuits (concerning ground). But this isn't technically true in the domain of high frequencies or low impedances. Since wires may be rearranged, an actual circuit does not have to appear exactly like its schematic representation.

1. In a circuit, the sum of the currents entering a point equals the sum of the currents out (conservation of charge). Kirchhoff's present law is a term used to describe this. A node is a term used by engineers to describe such a place. As a result, this may deduce the following: The current in a series circuit (a group of two-terminal devices linked end-to-end) remains constant.

2. When two components are connected in parallel, the voltage across them is the same. In other words, the sum of the "voltage drops" from A to B by one path via a circuit equals the sum of the "voltage drops" via any other route between A and B. This is sometimes described as follows: The sum of any closed circuit's voltage is always zero. This is termed referred to as   Kirchhoff's Voltage Law.

3. A circuit device's power consumption (work per unit time) is P = VI.

This is simply (work/charge) x (charge/ time). For V in volts and I in amps, P comes out in watts. Watts are joules per second (IW = IJ/s).

Usually, power is converted to heat, but it can also be converted to mechanical work (motors), radiated energy (lamps, transmitters), or stored energy (batteries, capacitors). Managing the heat load of a complex system (for example, a computer, where several kilowatts of electrical energy are converted to heat with the energetically inconsequential by-product of a few pages of computing output) can be a critical aspect of the process.

We'll have to expand the basic equation P = VI to deal with average power when dealing with regularly variable voltages and currents, but it's correct as a description of instantaneous power as is. Don't call current "amperage," by the way; that's bush-league. When we get to resistance, the word "ohmage" will be treated with the same discretion.