# Which Is Electric Current?

## What is Electric Current?

Electric current is defined as the rate of flow of electric charge in a conducting medium, typically measured in amperes or amps. Simply put, it refers to the movement of electric charge carriers, usually electrons, through a medium due to an applied electric voltage. An electric current flows when there is a closed conducting loop allowing charges to move continuously under the influence of an electric field.

Current can be defined as the rate at which an electric charge flows past a point on a conducting path. Electric charges flow because of the voltage difference between two points in a circuit. It is the electric potential difference that pushes or pulls the electric charges through the conducting path, enabling the current to keep flowing.

## DC vs AC Current

Current can flow in two ways in a circuit, either as direct current (DC) or alternating current (AC).

Direct current (DC) flows in one direction in a circuit. The current flows from the positive terminal of the battery, through the circuit components and back to the negative terminal of the battery. In a DC circuit the current remains flowing in the same direction.

Alternating current (AC) changes direction periodically in a circuit. The current will flow in one direction for a brief period, and then reverse and flow the other way for the same amount of time. The frequency of the current reversal ranges from 50-60 Hertz (or cycles per second) for AC power systems. Since the current is constantly reversing, the average voltage and current are zero.

In summary, DC flows consistently in one direction while AC alternates direction on a regular frequency.

## How Current Flows

Electric current is the result of electrons flowing through a conductor, such as a metal wire. This electron flow is caused by a voltage, also known as an electrical pressure or electromotive force (EMF), that generates an electric field in the conductor. Voltage acts as a sort of “push” to move electrons from the negative terminal to the positive terminal of a power source, creating an electrical circuit.

A useful analogy is to think of electric current like water flowing through a pipe. Water flows from high pressure to low pressure, just as electric current flows from high voltage to low voltage. The rate of water flow depends on the water pressure, and the rate of electric current depends on the voltage. Just as increasing the water pressure causes more water to flow, increasing the voltage in a circuit causes more current to flow. The volume of water flowing per second is analogous to the amperage, or amount of electric current. Furthermore, constrictions and friction in a pipe slow down water flow, just as resistance in wires hinders electric current.

## Resistance

When an electrical current flows through a conductor like a wire, it encounters resistance. Resistance is anything that obstructs or restricts the flow of current. Some materials like metals have very low resistance and allow current to flow easily. Other materials like rubber have very high resistance and severely limit current flow.

Resistance is measured in units called ohms. The higher the number of ohms, the higher the resistance and the more the material impedes the flow of electrons. Resistance is not necessarily a bad thing. We can take advantage of resistance to control and regulate current in electrical circuits and devices.

## Ohm’s Law

One of the most important relations in electricity and electrical circuits is Ohm’s Law. It states the following:

Voltage (V) = Current (I) x Resistance (R)

Where voltage is measured in volts, current is measured in amps, and resistance is measured in ohms. This simple but powerful equation describes the relationship between these three crucial electrical quantities.

Ohm’s Law allows us to make calculations and analyze circuits. If we know two of the values, we can calculate the third. For example, if we know the voltage applied to a circuit and the resistance, we can determine the current that will flow. The law also tells us that if we increase or decrease the voltage or resistance, it will affect the current.

Overall, Ohm’s Law is a foundational concept in electrical engineering and physics. It plays a critical role in circuit design, troubleshooting circuits when problems arise, and understanding how electric power systems function. The insight it provides into the behavior of electric current is invaluable.

## Measuring Current

Current is measured using a device called an ammeter. An ammeter is connected in series in a circuit to measure the flow of electric current. This allows the ammeter to directly intercept the flow of electrons through the circuit.

To properly measure current, the ammeter must have very low resistance. This is to ensure it does not alter the circuit it is measuring. An ideal ammeter would have zero resistance.

The basic working principle of an ammeter involves measuring the magnetic field produced by the current. The greater the current, the stronger the magnetic field produced. The ammeter detects this magnetic field and calculates the strength of the current flow.

Based on the scale of current being measured, different types of ammeters are used. For small currents up to a few amperes, moving coil instruments are commonly employed. For large industrial applications measuring hundreds of amperes, clamp meters are typically used.

Precision and sensitivity are important features of ammeters. Care must be taken to choose one appropriate for the expected range of current so accurate readings can be obtained.

## Factors Affecting Current

The electric current in a circuit depends on a few key factors. Two of the most important are voltage and resistance.

Voltage, which is measured in volts, represents the “push” or force driving the electric charges through a conductor. A higher voltage value will exert more force on the charges, causing them to move faster. This results in a larger electric current.

Resistance, measured in ohms, opposes the flow of electric charges. Materials like metal wires and carbon resistors impede the motion of the electrons somewhat. The higher the resistance value, the more the charges are slowed down. Therefore, increasing the resistance reduces the amount of current that flows.

So in summary, higher voltage causes more current, while higher resistance reduces the current. Understanding the relationship between voltage, resistance, and current is key to controlling the flow of electricity in circuits.

## Applications

Electric current plays an essential role in powering a wide variety of applications in our modern world.

### Electronics, Wires, and Batteries

Electronics like computers, phones, TVs, and appliances rely on electric current to operate. The current flows through the intricate circuitry and components inside electronic devices allowing them to perform their various functions. Wires and cables carry current to power electronics and electrical devices. Batteries act as portable sources of direct current, converting chemical energy into electrical energy.

### Electrical Power Transmission

Our electric power grids use high voltage alternating current to transmit electricity efficiently over long distances. The current is stepped up to extremely high voltages for power transmission through transmission lines and towers. It is then stepped down to lower voltages for distribution and use in homes, businesses, factories, and buildings. High voltage direct current (HVDC) transmission is also used for very long distance power transmission and for undersea cables.

## Safety

Electric current can be extremely dangerous if improperly handled. Some key safety precautions to take:

• Use circuit breakers – These will automatically cut off power if too much current flows through a circuit, preventing overheating and fires.
• Use GFCIs – Ground fault circuit interrupters can detect current leakage and cut off power to prevent electrocution.
• Beware of water – Never use electronics near water, which conducts electricity and increases shock risk.
• Insulate wires – Exposed wires can cause shocks or fires if they come into contact with people or flammable materials.
• Unplug appliances – Unplug appliances when not in use to prevent fires or shocks from damaged cords.
• Use proper PPE – Wear insulated gloves and shoes when working with electricity to avoid shocks.