What is an Electrical Conductor?
Electric current is the flow of electrons through a conductor. The movement of these charged particles creates a voltage or electrical potential difference between two points in a circuit. This potential difference can be harnessed to power electronic devices and appliances. In order to study electric current in conductors, it is important to understand how these electrons move and what factors affect their flow. By understanding the basics of electricity, you can more effectively learn about electric current in conductors and how to apply it in your own life.
Effect on the Flow of Electrons
There are several things that affect the flow of electrons through a conductor. The most obvious factor is the amount of current flowing through the circuit. This is measured in ampere (A) and can be affected by the resistance of the material as well as the number and size of the conductors. The resistance of a material is determined by its resistivity, which is a measure of how difficult it is for electrons to move through the substance. A higher resistivity means that there will be more resistance to the flow of current and vice versa.
What is Current?
When we apply a potential difference across any material, a flow of electrons (charges) takes place. The rate of flow of this electron is called current. If the material on which the potential difference is applied is a conductor, then we say this current to be the current in the conductor. If Q amount of charge flows through any cross-section of a conductor in time t, then- the current is defined as the rate of the flow of electrons, i.e
\[I = \frac{Q}{t}\]
The SI unit of the current is Ampere (A).
The current is mostly divided into two groups, i.e. alternating current and direct current, depending on the electric charge flow. In direct current, the charges flow through unidirectional while the charges flow in both directions in alternating current.
The Direction of the Current
As per the electron theory, when the potential difference is applied across any conductor in a circuit, some matter flows into it that actually constitutes the flow of current. It is believed that the matter flows from a high potential to a lower potential, i.e from the positive terminal to the negative terminal of the battery. Since the current has the direction, so technically, it should be a vector quantity because it has both the direction and value but in reality, it is a scalar quantity.
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Thus, conventionally the direction of current flow is from the positive terminal to the negative terminal of the battery.
Current in the Conductor
We all know that conductors are the substances that allow current to pass through them. When the conductor is not connected to the battery, the free electrons tend to move freely here and there. This electron moves randomly inside the conductor with a certain velocity. This velocity is called thermal velocity. Since the whole motion is random, the average velocity equals zero.
Next, the external electric field is applied. Once the battery is applied to the conductor, the electron starts moving towards the positive terminal of the battery. As the electrons move towards the positive terminal of the battery, it gets accelerated. Since the electron is moving in only one direction, it gets collides with the positive ions as well. With this collision, electrons tend to lose the velocity which they had gained because of the acceleration. Whenever any charged particle goes into any conductor, it doesn’t move into a straight line, it collides with the other charged particle. Because of this loss, a very small increase in velocity takes place. The average of this small gain in the velocity is called the Drift velocity. Drift velocity can be defined as the average of the velocity gained in a material due to an electric field.
\[V = \frac{I}{nAq}\]
Where,
v - Drift velocity
I - Electric current
n - no of electrons
A - Area of the cross-section of the conductor
q - charge of an electron in coulombs
Mobility of an Electron
The mobility of an electron is defined as the drift velocity of an electron for a unit electric field. The mobility depends upon the potential difference applied, conductor length, the density of charge carriers, current and area of the cross-section of the conductor.
\[\mu = \frac{V_{d}}{E}\]
Where, μ = mobility of an electron
Vd = Drift velocity of an electron
E = Electric field applied
Importance of Electric Current in a Conductor
The electric current in a conductor is important because of multiple reasons:
It is the means by which electronic devices and appliances are powered.
Without electric current, we would be unable to use many of the devices that we take for granted in our everyday lives. From computers and smartphones to televisions and refrigerators, all of these appliances require an electrical current in order to function. By understanding how electricity works, you can better utilize these devices and make your life a little bit easier.
Electricity is also responsible for powering many industrial applications. Factories use large motors to run their machinery, and these motors require a steady supply of electrical current. If there was no electric current in conductors, our world would look very different indeed.
FAQs on Electric Current in Conductors
1. What is meant by electric current in a conductor?
Electric current in a conductor is defined as the rate of flow of electric charge through any cross-section of that conductor. When a potential difference is applied across its ends, the free electrons start to drift in a specific direction, constituting a current. It is measured in Amperes (A).
2. How is the electric current in a conductor calculated using its formula?
The electric current (I) is calculated with the formula I = Q / t, where 'Q' is the total amount of charge passing through a cross-sectional area of the conductor and 't' is the time taken for this charge to pass. Another important formula relates current to drift velocity: I = nAevd, where 'n' is the number density of free electrons, 'A' is the cross-sectional area, 'e' is the charge of an electron, and 'vd' is the drift velocity.
3. Why are materials like copper and aluminium preferred for electrical wires?
Copper and aluminium are excellent conductors used for electrical transmission for two main reasons:
- Low Resistivity: They offer very little opposition to the flow of current, which minimises energy loss in the form of heat.
- High Abundance and Ductility: They are readily available and can be easily drawn into thin wires, making them cost-effective and practical for manufacturing electrical wiring.
4. How does an electric field cause a net flow of charge, or current, in a conductor?
In the absence of an electric field, the free electrons in a conductor move randomly, and their average velocity is zero. When an external electric field is applied (e.g., by a battery), the electrons experience an electrostatic force. This force causes them to accelerate and drift towards the positive terminal of the source. This collective, directional movement of electrons, superimposed on their random motion, is what constitutes a net flow of charge, or an electric current.
5. What is drift velocity and how does it relate to the electric current?
Drift velocity (vd) is the average velocity attained by charged particles, such as electrons, in a material due to an electric field. It is a very slow, directional movement. The relationship between current (I) and drift velocity is direct: a larger current implies a higher drift velocity for a given conductor. The formula is I = nAevd, showing that current is directly proportional to the drift velocity.
6. Why is electric current considered a scalar quantity even though it has a specific direction?
Although electric current has a magnitude and a direction (from higher to lower potential), it is a scalar quantity. This is because it does not obey the laws of vector addition, such as the parallelogram law. When two currents meet at a junction, the total current is found by simple algebraic addition (as described by Kirchhoff's Junction Rule), not by vector addition. Therefore, it lacks this defining property of a vector.
7. What is the fundamental difference between conventional current and the actual flow of electrons in a conductor?
The primary difference lies in their direction:
- Conventional Current: This is the historical convention. It is defined as the direction that positive charge carriers would flow. Therefore, its direction is from the positive terminal to the negative terminal of the power source.
- Electron Flow (or Electronic Current): This is the actual flow of charge in a metallic conductor. Since electrons are negatively charged, they are attracted to the positive terminal. Thus, the direction of electron flow is from the negative terminal to the positive terminal, which is opposite to the direction of conventional current.
8. If the drift speed of electrons in a conductor is very slow, why does a light turn on almost instantly when you flip a switch?
This is a common misconception. A light bulb turns on instantly not because the electrons from the switch travel to the bulb, but because the electric field propagates through the wire at nearly the speed of light. When you flip the switch, this electric field is established throughout the entire circuit almost instantaneously. This field exerts a force on all the free electrons already present in the bulb's filament, causing them to start drifting and produce light immediately.
9. What is meant by the mobility of charge carriers in a conductor?
Mobility (symbol μ) is a measure of how easily a charge carrier (like an electron) can move through a metal or semiconductor when an electric field is applied. It is defined as the magnitude of the drift velocity per unit electric field. The formula is μ = vd / E. A higher mobility means the charge carrier will move faster for a given electric field strength, indicating a better conductor.
10. How does the temperature of a conductor impact the electric current flowing through it?
As the temperature of a metallic conductor increases, the thermal vibrations of its atoms become more vigorous. This increases the frequency of collisions between the drifting electrons and the ions in the metallic lattice. These frequent collisions hinder the smooth flow of electrons, which effectively increases the conductor's electrical resistance. According to Ohm's Law (I = V/R), for a constant voltage, an increase in resistance will cause a decrease in the electric current.
