The Direct Current Cycle

A direct current (DC) refers to the electric charge that flows in one direction. A direct current passes through conductors such as wires, semiconductors, insulators or in a vacuum. In direct currents, electrons only migrate from a negatively charged area to a positively charged area in one direction. A battery is a prime example of a DC source. A special device called an inverter can convert direct current (DC) to alternating current (AC). A device known as a Rectifier can convert alternating current to direct current. Italian physicist Alessandro Volta was the first to produce direct current in 1800. Back then, the natural flow of electric current was not yet understood. Andre Marie Ampere was the scientist who put forward that DC flows in one direction from the positive terminal to the negative terminal. Previously, direct current was also known as galvanic current.

Definition Of Direct Currents

Direct currents can be defined in three different ways:

1. The phrase ‘direct current’ refers to a power system with only one polarity of either voltage or current. It flows unidirectionally. 
2. When passed through a circuit, it is a type of current that does not alter the direction, current and voltage, even though the supply may not be constant.
3. A direct current is an electrical circuit where all the currents and voltages are kept constant. The prime source of direct current is batteries.

Properties of Direct Currents

• One of the prime properties of direct currents is that there is no alteration in the polarity. 
• Even if there are large variations in the magnitude of the current, the direction of flow does not change. 
• Since voltage is not always ideally constant, noise is produced. Ripple is a common type of noise found in direct current voltages. 
• Direct current can be produced by using a commutator (a device that can generate direct current), using a rectifier (which converts AC to DC) and using the fundamental source, batteries.

How Do Direct Currents Work?

When protons and electrons were not yet discovered, Benjamin Franklin found something moving in a conductor. He assumed that the current flows from high concentration to lower concentration regions. He named the high concentration region the positive side and the lower concentration region the negative side. So, according to him, an electric current passed from the positive to the negative side. This is known as the conventional flow of current. After protons and electrons were revealed, it was verified that electrons move from the negative side to the positive side. The prime components of a direct current circuit are – a battery(source), ammeter(to measure current), voltmeter (to measure voltage), connecting leads and a switch. When current flows through this circuit, there is no alternation in polarity or direction. However, in reality, the voltage cannot be kept constant throughout the circuit and noise is generated. Ripple is the most common type of noise found in the circuit. 

Advantages and Disadvantages of Direct Currents 

Advantages 

• Direct current power can be produced from renewable forms of energy like solar energy. It does not generate any pollution like alternating current as it is complex in design. This is because alternating current uses energy from thermal and nuclear power plants.
• The direct current supply is more efficient as the magnitude and polarity are kept constant. The magnitude and polarity keep changing in alternating currents, so energy is not efficient.
• DC supply is more suitable for electronic circuits because the nature of direct current supply is constant.
• Direct current operated machines are more efficient than alternating current operated machines.
• Direct current supply has no noise, less power loss and no effects of inductance and capacitance.  
• Direct current electricity can be easily stored in batteries or supercapacitors.
• Transmission of direct current power is less expensive when compared to an alternating current power supply.

Disadvantages 

• The complexity of direct current generators is more compared to alternating current generators. DC cannot be produced at high voltages.
• DC cannot be transported over large distances because it cannot be stepped up or down.
• DC operated machines like DC motors and DC circuits breakers are more expensive than AC operated machines.
• The direct current voltage cannot be stepped up or stepped down easily.

Uses Of Direct Current 

Direct current is used in many areas such as – electrical, electronics, automobiles and even locomotives. The uses of direct current are elucidated below.

• Direct current is used in light-emitting diodes to generate light. 
• The direct current supply is applied to many low-voltage purposes, such as mobile batteries. It is utilised in emergency lighting, flat-screen TVs and more purposes in commercial buildings.
• A battery (DC) is used to start the engine, lights and ignition system in automobiles.
• DC is used in most communication and networking devices.
• High Voltage Direct Current (HVDC) constructs high voltage power transmission possible. High Voltage Alternating Current (HVAC) has many disadvantages over HVDC, such as the corona effect or skin effect.
• Locomotive engines always run on direct current. In diesel locomotives, fans, lights and sockets work on direct current.

Conclusion  

In a direct current, electric charges flow unidirectionally. A battery is a prime example of a DC source. A chief property of direct currents is that there is no alteration in the polarity. Italian physicist Alessandro Volta was the first to produce direct current in 1800. When protons and electrons were yet to be discovered, Benjamin Franklin discovered something moving in a conductor. According to him, an electric current passed from the positive to the negative side. This is known as the conventional flow of current. After the discovery of protons and electrons, it was confirmed that electrons pass from the negative to the positive side. Direct currents have several advantages and disadvantages. They have numerous applications in commercial buildings, automobiles, high voltage power transmissions, diesel locomotives, etc.