Types of Current: Direct and Alternating Current, Other Types and Sample Questions

There are mainly two types of current, namely direct current (DC) and alternating current (AC). The alternating current flows in two directions, while the direct current flows in one direction. Electrons move in one direction with a direct current. Batteries produce direct current. In alternating current, electrons flow in both directions.

Read More: Difference between Earth and Neutral

Keyterms: Direct Current, Alternative Current, Current Transformer, Steady Current, Instantaneous Current, Varying Current, Current, Electricity, Electron, Battery

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Types of Current

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Current can be defined as the flow of charged particles through a conducting medium, such as a wire. When we talk about electricity, the charged particles we're referring to are almost always electrons which are an integral part of electricity. So, there are two forms of electric current:

1. Direct Current (DC)
2. Alternative Current (AC)

Direct Current (DC)

DC current is current that flows in one direction at a constant rate. In a closed-circuit loop, both electrons travel in the same direction around the loop. The majority of circuits connected to the battery create this type of current. This is because batteries are intended to only enable electrons to travel in one direction through a conducting wire (as opposed to flowing through the battery itself, in the opposite direction) from their anode (negative terminal) to their cathode (positive terminal). The frequency of Direct Current is ZERO since it travels in the same direction.

Check Out: Current Electricity

Alternating current (AC)

Alternating current is an electrical current whose direction and value change over time (AC). The value of AC current grows in one direction from ZERO to MAXIMUM and then decreases to ZERO, and then increases in the opposite direction from ZERO to MAXIMUM and returns to ZERO. The graph of AC resembles a wave because of the growth in both directions. This is known as a sine wave. In Alternate Current or AC, there are 50 such cycles or waves in ONE second. The AC is PHASE on one side and NEUTRAL on the other.

Other Types of Current

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• Steady Current- A constant current (also known as a steady current, time-independent current, or stationary current) is a form of direct current (DC) that does not alter in intensity over time.
• Instantaneous Current- It referred to the present value at a specific point in time. Charging and discharging currents are the two forms of current. The rate of flow varies with time in this case, which is measured in milli seconds.
• Varying Current- The magnitude of the stream varies with time, but the direction remains constant.

Read More: Electrical Resistance 

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What is Electrical Current?

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Electrical current defines the flow of electrons in an electric circuit, where a complete circuit can be thought of as a closed loop. Electrons that move through a closed loop of an electric circuit are in the “current” that can be thought of as a type of charge. All of the current that moves in a closed loop of the circuit is considered a complete “current.” Current basically flows from an object’s negative to its positive. It is measured with the use of either ammeters or resistors.

Read More: Current Electricity Important Questions

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The Value of Current

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Current is the measure of the number of charges moving through an allotted time. Generally, the larger the current, the greater the charge moving through a given time. It is often denoted by 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.

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Current Transformers of Various Types

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The Current Transformer (C.T.) is a sort of "instrument transformer" that creates an alternating current proportionate to the current measured in its main winding in its secondary winding. Current transformers reduce high voltage currents to a tolerable level, allowing a standard ammeter to track the actual electrical current flowing in an AC transmission line safely. A simple current transformer differs from a traditional voltage transformer in that it operates on a different principle.

Bar, wound, and toroidal current transformers are the three types of current transformers.

• Bar-type Current Transformer- This sort of current transformer's primary winding is the main circuit's actual cable or bus bar, which is comparable to a single switch. They are typically bolted to the current-carrying unit and are entirely protected from the high operating voltage of the system.
• Wound Current Transformer - The primary winding of the transformer is physically linked in series with the circuit's current conductor. The magnitude of the secondary current is determined by the transformer's turn ratio.
• Toroidal Current Transformer- A toroidal current transformer does not have a primary coil. Instead, a line threaded through a window or hole in the toroidal transformer carries the current flowing through the network. Some current transformers include a "split heart" that allows them to be opened, assembled, and closed without disrupting the circuit they are attached to.

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Current Electricity Ncert Solutions

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Current Meter Types

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1. Rotor current meters
2. Tilt current meters
3. Doppler and Travel Time current meters

1. Rotor current meters are mechanical current meters that rely on the rotations of a propeller to calculate the current. The Ekman current meter, which counts the number of rotations by dropping balls into a jar, is a mid-twentieth-century invention. The Roberts radio current meter is a moored buoy-mounted equipment that transmits data through radio to a servicing vessel. Savonius current meters spin around a vertical axis to minimize the inaccuracy induced by vertical motion.
2. Tilt current meters function on the drag-tilt principle and can float or sink depending on the kind. A flexible rope or tether in a floating tilt current meter is commonly used to secure a subsurface buoyant housing to the seafloor. The meter is suspended from the connecting point in a sinking tilt current, which is similar to a rising tilt current.
3. The two most prevalent acoustic current meters are Doppler and Travel Time. Both systems use a ceramic transducer to transmit sound into the water. Doppler instruments are becoming more popular. The Acoustic Doppler current profiler (ADCP) is one such instrument, which employs the Doppler effect of sound waves distributed back from particles within the water column to calculate water current velocities over a depth range. Travel time sensors calculate water velocity using at least two acoustic impulses, one upstream and one downstream.

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Things to Remember

• The two forms of current electricity are direct current (DC) and alternating current (AC). Electrons can only go in one direction with a direct current. Direct current is generated by batteries. Electrons move in all directions in an alternating current.
• While AC current is ideal for long-distance transmission, DC current is ideal for digital electronics.
• Inverters and transformers can even convert a specific DC input voltage are converted to a completely different AC output voltage (higher or lower), but the output power must always be less than the input power: An inverter and transformer can't output more power than they take in due to energy conservation, and some energy is wasted as heat as electricity flows. In actuality, an inverter's efficiency is typically over 90%, yet fundamental physics tells us that some energy is still squandered somewhere, no matter how modest.

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Previous Year Questions 

1. When a wire of uniform cross-section a, length l and resistance R is bent into a circle...[NEET 2005]
2. If these resistances were connected in series, the combination would have a resistance in ohms, equal to….[NEET 2004]
3. Electric power is sent from one city to another city through copper wires. The fall of potential…..[NEET 2004]
4. In the circuit shown in the figure, if the potential at point AA is taken to be zero, the potential at point  B is..[NEET 2011]
5.  student measures the terminal potential difference (V) of a cell as...[NEET 2009]
6. The potential difference per unit length of the wire will be… [ NEET 1999 ]
7. Value of R for which the power delivered in it is maximum is given by... [ NEET 1992 ]
8. In the circuit shown below, the current in the 1Ω resistor is…? [NEET 1988]
9. In the network shown in the figure, each of the resistance is equal to…? [NEET 1995]
10. Kirchhoff's first and second laws of electrical circuits are consequences of…? [NEET 2006]
11. Two wires of the same metal have same length, but their cross-sections are in the ratio…? [NEET 1995]
12. Which of the following acts as a circuit protection device? [NEET 2019]
13. If now we hav.e to change the null point at 9^th  wire, what should we do?… [ DUET 2007]
14. The electrical permittivity and magnetic permeability of free space are​… [ DUET 2003]
15. Just after key K is pressed to complete the circuit, the reading will be​ …. [ KEAM 1999]