What is a Coulomb?
A coulomb
(C) is the unit of electric charge in the International System of Units (SI).
It represents the quantity of electric charge carried by a certain number of
electrons.
Definition
of Coulomb
One coulomb is the amount of charge transferred by a current of one ampere in one second.
1C=1A×1s
Q=It
This means that if a current of 1 ampere flows through a conductor for 1 second, the total charge moved is 1 coulomb.
Coulomb
and Elementary Charge (Electron Charge)
Since
electrons carry charge, we can relate coulombs to electrons:
- Charge of one electron:
e=1.602×10−19C
- Number of electrons in one
coulomb:
1C=1.602×10−191=6.242×1018 electrons
This means
that one coulomb of charge is equivalent to the charge of approximately 6.242 ×
10¹⁸ electrons.
Force is a
push or pull acting on an object that can cause it to move, stop, or change
direction. It is a vector quantity, meaning it has both magnitude and direction.
SI Unit of Force: Newton (N)
The unit
of force is the Newton (N), named after Sir Isaac Newton.
This means one newton is the force required to accelerate a 1 kg object at a rate of 1 m/s².
Newton’s Second Law of Motion (Force
Formula)
Newton’s
second law states that force is the product of mass and acceleration:
- F = Force (in Newtons, N)
- m = Mass (in kilograms, kg)
- a = Acceleration (in meters
per second squared,
)
Work
The unit
of work or energy is the joule (J) where one joule is one newton meter.
The joule is defined as the work done or
energy transferred when a force of one newton is exerted through a distance of
one meter in the direction of the force.
W = Fs
Current
The
current is the flow of current.
Thus,
current can be measured by measuring how many electrons are passing through
material per second.
The flow
of charge per unit time is used to quantify an electric current.
𝐼 = 𝑄 𝑡 𝐴𝑚𝑝𝑒𝑟𝑒
Electric Potential and Potential
Difference
v Electric Potential
Electric
potential is the ability of a charged particle to do work due to its position
in an electric field. It is the amount of work done in bringing a unit positive
charge from infinity to a specific point in an electric field.
v Unit of Electric Potential (Volt)
The SI
unit of electric potential is the Volt (V).
v Potential Difference
Potential
difference (Voltage) is the difference in electric potential between two points
in a circuit. It represents the energy required to move a charge between two
points.
Example:
If a battery
has a potential difference of 12V, it means 12 joules of energy are used to
move 1 coulomb of charge through the circuit.
v Electromotive Force (EMF)
- EMF is the energy supplied per
unit charge by a battery or generator.
- It is measured in volts (V)
and represents the maximum voltage a power source can provide.
Example:
- A 12V battery has an EMF of 12
volts, meaning it provides 12J of energy per coulomb of charge.
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