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Electric Fields Chemistry

Electric Fields Chemistry

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Have you ever thought about why lightning strikes during a storm? Or why electrons revolving around an atom's nucleus don't fly away even though they're moving super fast? It's because of something called an electric field in chemistry. This phenomenon is responsible for both lightning and the stability of atoms.

Electric fields definition

An electric field is a space around an electric charge where another electric charge will feel a force. This force is measured in units of NC-1 (Newtons per Coulomb). Electric charges attract or repel each other based on their charges, just like magnetic poles. A positively charged particle attracts a negatively charged particle and repels another positively charged particle. The force on charges in an electric field is given by the formula F = Eq, where F is the force, E is the electric field's magnitude, and q is the point charge. The equation tells us that a larger charge experiences a larger force. Electric fields can be seen through electric field lines. Positive particles emit electric field lines, while negative particles attract them. The fields of positive particles continue on infinitely, while the fields of negative particles converge on the particle itself.

Electric Field around a Point Positive Charge
Electric Field around a Point Positive Charge
Electric Field around a Point Negative Charge
Electric Field around a Point Negative Charge

 

 

A vector is a quantity that has both magnitude and direction, while a scalar quantity only has magnitude. Electric fields can also be visualized using vectors. The electric field at any point is the sum of all electric field vectors. Electric fields have properties like electric field lines never intersecting each other. Electric fields are stronger where the lines are closer together and always perpendicular to the charged surface. The number of lines is proportional to the electric charge. Electric field lines start from positive charges and end at negative charges. Magnetic fields, on the other hand, have north and south poles. Magnetic field lines emerge from the north pole and converge into the south pole, forming closed loops. Unlike magnetic fields, electric charges can exist as isolated positive or negative charges.

Types of electric fields

There are two types of electric fields.

Uniform electric field

As the name suggests, an electric field is called uniform when it does not change over distance. A charge (q) would experience the same magnitude and direction of force at any point in a uniform electric field. As an example, consider the electric field between two oppositely charged parallel plates, as shown in the figure below.

Uniform Electric Field Lines
Uniform Electric Field Lines

Non-uniform electric field

Again, as the name implies, a non-uniform electric field is not constant and can vary from point to point. A charge (q) would experience varying magnitude or direction (or both) of force at different points, in a non-uniform electric field. Consider the example below, which shows an electric field from a single point charge.

Non-uniform Electric Field Lines
Non-uniform Electric Field Lines

Electric fields emanating from subatomic charged particles (electrons and protons) hold an atom together. Without them, the atom would cease to exist, and by extension, everything else as well. Electric fields are also responsible for molecular interaction in chemical reactions.

Coulomb's law

Coulomb's law states that like charges repel and unlike charges attract each other. The force of attraction (or repulsion) between two point charges is inversely proportional to the square of the distance between them and directly proportional to the product of the two charges. The formula for the force between two point charges is given by F = k(q1q2)/r^2, where k is the proportionality constant and ε₀ is the permittivity of vacuum with a value of 8.854 Nm2C-2. The value of k is 9*10^9 Nm2C-2. By using this formula, we can find the electric field strength due to a charge q1 at a point r.

Causes of electric fields

An electric field is formed when there is a difference of electric potential between two points in space. Electric potential is the amount of work needed to move a unit charge from infinity to a point in an electric field. The electric potential at a point at a distance of r from the charge Q is directly proportional to Q and inversely proportional to r. The electric potential can be expressed as Velec = kQ/r, where k is the proportionality constant and ε₀ is the permittivity of vacuum. By differentiating Velec with respect to r, we can obtain the formula for the electric field. To create a small electric field, we can rub a plastic ruler or comb on our hair or a piece of cloth to acquire a static negative charge which has a static electric field around it. This creates a potential difference between the ruler and paper, resulting in a force towards it. Electric fields are vector quantities while electric potential is a scalar quantity.

Electric potential energy

Electric potential energy is the energy required to move a charge through an electric field or the total energy required to hold a system of two charges in a particular configuration, due to the electrostatic forces between the two charges. The electric potential energy of a system of two point charges q1 and q2 separated by a distance r is given by Uelec = (kq1q2)/r. When the charges are very far apart, the potential energy is 0. The work done on the charges to bring them at a distance of r is stored as potential energy in the system. The work done by the electrostatic forces of charges is equal to the negative of potential energy. The potential energy required to hold one charge at a distance of r from another charge can be obtained by multiplying electric potential by charge q. The unit of electric potential energy is Joules.

To summarize, an electric field is a region around a charged particle in which other charged particles will experience a force. Electric fields can be visualized with electric field lines, much like magnetic field lines. When a single positive point charge is present, electric field lines will emerge from the point charge and end at infinity, while a single negative point charge will have electric field lines start at infinity and end at the point charge. A uniform electric field has uniform intensity at every point in space, while a non-uniform electric field intensity can vary from point to point. Coulomb's law quantifies the force of attraction between two charged particles, while electric field is the result of electric potential difference between two points in space. Finally, the work done on a system of charges to assemble them in proximity of each other is stored in the system as its potential energy.

Electric Fields Chemistry

What is an example of electric field? 

The nervous system of the body uses electric fields to transmit electrical signals from one neuron to another. Another example would be lightning strikes, which result from strong electric fields due to static charge build-up on the ground and in clouds during a storm.

What does an electric field strength depend on?

Electric field strength depends on the magnitude of source charge, and the distance from it.

What is electric field? 

Electric field is the region around a charged particle in which other charged particles will experience a force.

What are the types of electric field? 

1. Uniform electric field2. Non-uniform electric field

How are electric fields used in real life? 

Electric fields are used in capacitors in electronics.

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