Types of Current

In nature, as an example, the current may originate in the sun’s energy as negatively charged particles; they move to earth through our atmosphere; and, in our bodies, they can produce a life-like sensation in some of our nerve cells. Currents can also be controlled by the action of other charges, as well as the properties of the object itself. Because of these properties, current flow occurs either naturally or by controlled electrical means. Electrical current has many applications in everyday life. It is used to make electricity, generate voltage, move charges, and detect objects.

Applications of Current

Many of the applications of current flow, such as electricity, have their own characteristics. Current has many purposes and applications. Many of the electrical phenomena of the human body, for example, are related to the flow of current. Electricity is used in many other applications, from powering our homes to the creation of the world wide web. Current also serves as a means of detection by our bodies. For example, we know when an object, such as our finger, touches a conducting surface.

Electrical Current

Electrical current is the flow of electrons in an electric circuit. A complete circuit can be thought of as a closed-loop. Electrons that move through a closed-loop (or a “path”) of an electric circuit are in the “current.” Current can be thought of as a type of charge, much like the flow of water is a type of flow of water, but much smaller and quicker. All of the current that moves in a closed loop of the circuit is considered a complete “current.”

The Direction of Current

Current flows from an object’s negative to its positive. It is important to remember this rule because it makes measuring current relatively simple. It can be measured with the use of either ammeters or resistors.

The Value of Current

Current is a measure of the number of charges moving through a given amount of time. In general, the larger the current, the greater the charge moving through a given amount of time. It is often expressed in amperes (abbreviated as amps). 1 amp (or 1 A) is equal to one ampere. For example, a 10-amp fuse or light bulb has 1 A of current flowing through it.

Measurement of Current

Current can be measured in either one of two ways. It can be measured directly by measuring the flow of charge through an object, or it can be calculated by measuring the power output of an object or by using a variable resistor.

A constant can be used as a measurement of the flow of current. A meter, such as a meter stick or volt-ohm meter, is one way to measure current. A volt-ohmmeter is a voltmeter that measures current in addition to other measurements. A volt-ohm meter can be thought of as a more versatile voltmeter. It is sometimes called an ammeter because it also measures amperage (amps).

If the measured current is constant and of a certain level, the constant measurement can be used to determine current. To do so, multiply the constant by the level of current. If the constant is 1 ampere and the current is 10 amps, then the current is 100 amperes. To calculate current, use the current in the formula below.

Amperage (amp) = Current (amps) / Constant (Amp)

Calculating Current

Current can also be calculated. To calculate current, add the current with the constant. In the following example, the current is 1 amp and the constant is 10 amps, so the current is 10 amps.

• 10 amps = 1 amp

• 10 amperes = 1 A

Current is usually measured by multiplying the current with the constant (1 amp by 10 amps). If the constant is zero (such as in the case of the voltage meter), the term in parentheses (current or amps) will be zero. The result will be a number, which can be expressed as a ratio. A good way to express a current in terms of a ratio is as follows:

• 10 amps = 10 / 1

• A = 10 amps

Current can be expressed in ratios, a special type of formula that represents a fraction of the total current, the denominator of the fraction represents the entire current in the total calculation. When the denominator is zero (as it is for the voltage, amps, or ohms of a meter), the term in parentheses (current or amps) will be zero. A fraction such as this represents the current as a fraction of the total current. In the following example, the current is 1 amp, and the denominator is 1 amp, so the current divided by 1 amp equals 100%. In the following example, the denominator is 10 amps, and the numerator is 1 amp, so the current is 1 amp divided by 10 amps equals 10%. To convert from a current ratio to a fraction, multiply the constant by the numerator, and divide the constant by the denominator.

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.

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).

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.

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 current transformers 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, 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

Rotor current meters are mechanical current meters that depend on counting the rotations of a propeller. The Ekman current meter, which drops balls into a jar to count the number of rotations, is a mid-twentieth-century realization. The Roberts radio current meter 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 meters rotate around a vertical axis.

Doppler and Travel Time acoustic current meters 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.

Tilt current meters 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 meter. A sinking tilt current is equivalent to a rising tilt current, except the meter 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.