Goals
1. Get to grips with the relationship between electric charges, distance, and the resulting electric force.
2. Apply Coulomb's Law to tackle real-world problems involving forces between point charges.
Contextualization
Coulomb's Law is a key concept for understanding how electric forces operate between charges. A down-to-earth example is when we rub two balloons on our hair and see them repel each other when brought close together. This everyday occurrence is explained by Coulomb's Law, which illustrates the force of attraction or repulsion between charged particles. Grasping this law is crucial for numerous applications, spanning from electrical engineering to communication technology, where manipulation of electric charges is essential.
Subject Relevance
To Remember!
Coulomb's Law
Coulomb's Law describes the force of attraction or repulsion between two point electric charges. This force is directly proportional to the product of the charges and inversely proportional to the square of the distance separating them. The formula is F = k * (|q1 * q2|) / r^2, where F is the force, q1 and q2 are the charges, r is the distance between them, and k is Coulomb's constant.
-
The force is directly proportional to the product of the charges.
-
The force decreases as the distance increases, following an inverse square relationship.
-
Coulomb's constant (k) in a vacuum is around 8.99 x 10^9 N·m²/C².
Relation Between Force, Charges, and Distance
The electric force between two charges is influenced by the size of the charges and the distance between them. If the distance increases, the force drops off rapidly due to the inverse square relationship. The nature of the force (whether it’s attractive or repulsive) also varies depending on the charges: opposite charges attract, while charges of the same sign repel each other.
-
Attractive forces occur between charges of opposite signs.
-
Repulsive forces occur between like-sign charges.
-
The force declines as the distance between charges increases.
Practical Applications of Coulomb's Law
Coulomb's Law finds its way into numerous technologies and devices we use daily. For instance, proximity sensors in smartphones leverage principles of Coulomb's Law to detect nearby objects. Additionally, semiconductor device manufacturing and electronic circuit design are grounded in the manipulation of charges and electric forces.
-
Proximity and touch sensors in mobile devices.
-
Development and manufacturing of semiconductor devices.
-
Design of electronic circuits.
Practical Applications
-
Touch sensors in smartphones utilise Coulomb's Law to detect the closeness of fingers or objects.
-
Medical equipment, like defibrillators, employs Coulomb's Law principles to create and manage electric fields.
-
Communication technologies, such as antennas and transmitters, depend on manipulating electric charges to relay signals.
Key Terms
-
Electric Charges: Properties of particles that lead to forces of attraction or repulsion.
-
Electric Force: The force acting between two charged particles, as described by Coulomb's Law.
-
Coulomb's Constant (k): A proportionality constant in Coulomb's Law formula, around 8.99 x 10^9 N·m²/C².
Questions for Reflections
-
How can a grasp of Coulomb's Law drive the creation of new technologies?
-
In what other everyday situations, besides the examples given, can you spot the application of Coulomb's Law?
-
How can the manipulation of electric charges help resolve modern issues in electronics and telecommunications?
Practical Challenge: Measuring Electric Force
This challenge aims to solidify your understanding of Coulomb's Law through a hands-on experiment that allows you to visualise the electric force between two charges.
Instructions
-
Gather the necessary materials: two balloons, a piece of fabric (like wool or cotton), and a ruler.
-
Rub the balloons on the fabric to give them an electric charge.
-
Suspend one of the balloons so that it can hang freely and move.
-
Slowly bring the second charged balloon close to the suspended one and note how they interact.
-
Use the ruler to measure the distance between the balloons at the point where the force of repulsion or attraction is most apparent.
-
Record your observations on the electric force and the distance between the charges.
-
Based on your observations, calculate the electric force using Coulomb's Law (F = k * (|q1 * q2|) / r^2).
