# Types of Current

## Introduction

The movement of electrons produces electricity. The negatively charged electrons in atoms travel about spontaneously in all substances. The product of electrons moving in a specific direction inside a material or from one entity to another is electricity. Electron movement can be used to generate electricity. When two objects are rubbed together, electrons are moved from one object to another, resulting in static electricity. The electricity is called electric current as electrons flow in a current, such as through a conductor or copper wire.

There are mainly two different types of current: Direct current and alternating current.

1. Direct Current - or DC, is current that flows at a constant rate in one direction. Both electrons in a closed-circuit loop pass in the same direction around the loop. This is the type of current that most circuits connected to the battery produce. This is due to the fact that batteries are designed to only allow electrons to flow in one direction from their anode (negative terminal) to their cathode (positive terminal) through a conducting wire (as opposed to flowing through the battery itself, in the opposite direction).

2. Steady Current: A constant current (also known as a steady current, time-independent current, or stationary current) is a type of direct current (DC) whose intensity does not change over time.

3. Alternating Current- AC stands for alternating current, which oscillates and shifts direction at a fixed frequency. The number of oscillations per second is calculated in hertz (Hz), with 1 Hz equaling 1 second-1.

This article will study different types of current, types of ocean currents and types of the current transformer in detail.

## Types of Ocean Currents

Ocean circulation gets its energy from two sources at the sea surface, which result in two types of ocean currents

(1) wind-driven circulation, which is induced by wind stress on the sea surface, and

(2) thermohaline circulation, which is induced by changes in water density imposed at the sea surface by the interaction of ocean heat and water with the atmosphere, which results in a buoyancy exchange. Since wind speed affects sea-air buoyancy and momentum exchange, these two circulation forms are not completely separate. Wind-driven circulation is the more powerful of the two, creating gyres that dominate an ocean area.

### Different Types of Current Transformer

The Current Transformer ( C.T.) is a type of "instrument transformer" that produces an alternating current in its secondary winding that is proportional to the current measured in its primary. Current transformers minimize high voltage currents to a manageable amount, allowing a typical ammeter to safely track the real electrical current flowing in an AC transmission line. A simple current transformer works on a slightly different concept than a conventional voltage transformer.

There are three types of current transformer: wound, toroidal, and bar.

1. Wound Current Transformer – The primary winding of the transformer is physically connected in series with the conductor that holds the circuit's measured current. The magnitude of the secondary current is determined by the transformer's turn ratio.

2. Toroidal Current Transformer- A primary winding is not present in a toroidal current transformer. Instead, the current flowing through the network is carried by a line threaded through a window or hole in the toroidal transformer. Some current transformers have a "split heart" that allows them to be opened, assembled, and closed without interrupting the circuit they are connected to.

3. Bar-type Current Transformer- The primary winding of this type of current transformer is the actual cable or bus-bar of the main circuit, which is equivalent to a single switch. They are normally bolted to the current-carrying unit and are completely shielded from the system's high operating voltage.

### Types of Current Meter

1. Rotor current metres are mechanical current metres that depend on counting the rotations of a propeller. The Ekman current metre, which drops balls into a jar to count the number of rotations, is a mid-twentieth-century realisation. The Roberts radio current metre is a system that is mounted on a moored buoy and sends its data to a servicing vessel via radio. To reduce the error introduced by vertical motion, Savonius current metres rotate around a vertical axis.

2. Doppler and Travel Time acoustic current metres are the two most common models. A ceramic transducer is used in both methods to emit sound into the water. The use of Doppler instruments is more popular. The Acoustic Doppler current profiler (ADCP) is one such instrument, which uses the Doppler effect of sound waves dispersed back from particles within the water column to determine water current velocities over a depth range. At least two acoustic signals, one upstream and one downstream are used by travel time instruments to calculate water velocity. The average water speed between the two points can be measured by precisely calculating the time it takes to pass from the emitter to the receiver in both directions. Water velocity can be calculated in three dimensions using different paths.

3. Tilt current metres work on the drag-tilt principle and, depending on the type, are designed to float or sink. A subsurface buoyant housing is usually fixed to the seafloor with a flexible line or tether in a floating tilt current metre. A sinking tilt current is equivalent to a rising tilt current, except the metre is suspended from the connection point.

### Did You Know?

Inverters and transformers may even be used to convert a certain DC input voltage into a completely different AC output voltage (either higher or lower), but the output power must always be less than the input power: conservation of energy dictates that an inverter and transformer can't give out more power than they take in, and some energy is inevitably lost as heat as electricity flows. In reality, an inverter's efficiency is frequently over 90%, while fundamental physics informs us that some energy—however small—is still wasted somewhere.