Electric Current - Definition, Types, Applications, FAQs

Electricity is the flow of charge through a material in an electric current, usually expressed in amperes. In current electricity behaviour, its movements are mostly a result of the movement of electrons through a conductor such as a wire. A pressure difference, which can be likened to an electric pressure, initiates this flow as it forces electrons along a path with low resistance. The existence of electrical devices that help in facilitating life atoms’ motion and operation of current technological advancements depends largely on this movement of electrons. In this article we will discuss the concept of electric current, it is a keystone to different technologies and applications.

What is an Electric Current?

Electric current is defined as the rate of flow of electric charge through any cross-section.

i.e If a charge flows through an area for time $\Delta t$ then average electric current through the area is defined as-

$\bar{i}=\frac{\Delta Q}{\Delta t}$

The instantaneous current at any time t is given by

$ i=\lim _{\Delta t \rightarrow 0} \frac{\Delta Q}{\Delta t}=\frac{d Q}{d t}$

If the flow is uniform then the Current

$ I=\frac{Q}{t} $

If a current I flows through an area for time t then, the total charge flowing is

$Q=\int I d t$

Till now we have studied the current now will study about it's direction.

Properties of Electric Current

• An electron flow in the circuit is what causes current.
• By adding resistance to the circuit, it is possible to regulate the flow of electric current.
• Amperes are used to measure electric current (A). One coulomb of charge can be moved in one second at a rate of one ampere.
• In a circuit, electrical current flows from higher electric potential to lower potential (from the positive terminal to the negative terminal), often referred to as the traditional direction of current flow.

Also, read

• NCERT Solutions for All Subjects
• NCERT Notes For All Subjects

The Direction of the Current

As Current is the rate of flow of charge, Charge can be +ve or -Ve.

The direction of positive charge flow is considered the conventional direction of current. The direction opposite to the direction of the flow of negative charge is considered the conventional direction of the current.

Current flows through a circuit only if the circuit is closed.

For a Closed-circuit

1. Conventional current: Positive terminal to negative terminal

2. Electron current: Negative terminal to Positive terminal

Properties of Electric Current

• Current can be added algebraically.

• Current is a tensor quantity ( if in options tensor is not given take current as scalar quantity)

• Unit of Electric Current: The unit of electric current is Ampere or A.

The current is said to be 1 ampere when 1 coulomb of charge flows through any cross-section in every second.

Calculating Current in Different Situations

1. When the charge is performing translatory motion

• $\text { If } n \text { particles each having charge } q \text { pass a given area in time } t$

$$i=\frac{n q}{t}$$

2. When the charge is performing rotatory motion

If a point charge q is moving in a circle of radius r With Velocity V (frequency $\nu$, angular speed $\omega$ and time period T ). Then,

$ i=\frac{q}{t} \Rightarrow \frac{q}{T}=q \nu=\frac{q V}{2 \pi r}=\frac{q w}{2 \pi}$

Related Topics

• Amperes Law
• Circuit Diagram
• Conductors and Insulators
• Electric Circuit
• Electric Power

Types of Current

1. Alternating current

• Magnitude and direction both vary with time.

• Shows a heating effect only.

• Its symbol

2. Direct current

• No change in magnitude and direction with time.

• Shows the heating effect, chemical effect, and magnetic effect of current.

Current Independent of Area

Current does not change with change in cross-sectional area

Here $i_1=i_2=i_3$

Effects of Electric Current
Electricity has three main effects:

• Heating effect

• Magnetic effect

• Chemical effect

Heating Effect

Heat is typically produced when current flow is resisted. This is so that electrons can overcome resistance while passing via a wire or resistor. To overcome the Electrical resistance, which is transformed into heat energy, work must be done. It is the basis for all electric heating devices, including toasters, water heaters, and iron. Even connecting wires provide some minimal current flow resistance. This is the reason why, when utilized in an electric circuit, practically all electrical gadgets and connected wires feel warm.

The heating effect is given by the equation:

$$
H=I^2 R t
$$
As a conductor produces more heat the longer that current travels through it. The conductor's electrical resistance and the heat generated increase with resistance i.e. how much current there is the amount of heat produced increases with increasing current. The quantity of heat produced by a tiny current will probably be negligible and may go unnoticed. The generation of appreciable heat is conceivably feasible, though, if the current is greater.

Magnetic Effect

The movement of electrons is all that constitutes an electric current, and as is well known, while charges are resting, they produce an electric field, and when charges are moving, they produce a magnetic field. The presence of a magnetic field produced by the electric current causes the needle to deflect when a metallic sheet is inserted into a wire with electricity flowing through it. Electromagnets, which are created with the aid of electric current, are one of the most common uses of the magnetic effect of electric current. A conductor or wire-carrying current creates a magnetic field that is perpendicular to the direction of the field.

Chemical Effect

A solution ionizes or separates into ions, whenever an electric current flows through it. This is due to the fact that when an electric current flows through the solution, a reaction occurs. The developments and associated effects can be seen in the solution, depending on the type of electrodes used and the composition of the solution.

Solved Examples Based on Electric Current

Example 1: One billion electrons pass from A to B in 1 ms. What is the direction and magnitude of the current?

1) 1.6 A

2) 0.8 mA

3) 0.16$\mu$A

4) 1.6 mA

Solution:

Translatory motion of charge

i=n q A

wherein

If $n$ particles charge $q$ pass per second per unit area, the current associated with a cross-section area $A$ is:

$i=\frac{N e}{t}=\frac{\left(10^9\right)\left(1.6 * 10^{-19} \mathrm{C}\right)}{10^{-3}}=1.6 * 10^{-7} \mathrm{~A} $
i = 0.16 m A.

The current flows from B to A.

Hence, the answer is the option (3).

Example 2: The average value of a sinusoidal A.C. current over one cycle is:

1) Positive

2) Negative

3) Zero

4) Can be positive negative or zero.

Solution:

Alternating current

magnitude and direction both vary with time

wherein

The average of sinusoidal A.C. current over one cycle is zero.

Hence, the answer is option (3).

Example 3: Alternating current can

1) produce a heating effect

2) Be used for Charging of battery

3) can be used for electrolysis

4) All of the above

Solution:

Alternating current

Shows a heating effect only.

A.C. current cannot be used for electrolysis or battery charging as its average value is zero.

Hence, the answer is the option (1).

Example 4: Direct current has

1) Both magnitude and direction constant

2) only magnitude constant

3) only direction constant

4) None of the above

Solution:

Direct current

No change in magnitude and direction with time.

wherein

Direct current has their direction constant. i.e. it cannot reverse its direction.

Hence, the answer is option (3).

Example 5: Which of the following effects can be shown by both direct current and alternating current?

1) Magnetic effect

2) heating effect

3) Chemical effect

4) Charging of battery

Solution:

Alternating current Shows a heating effect only.

But direct current Shows the heating effect, chemical effect and magnetic effect of current.

Hence, the answer is the option (2).