Page 1 of 4
Page 1 of 4
Imaging Equipment and Maintenance
Topic 1: Basic Concepts of Electricity
Electric Charges
• Electric charges can be positive or
negative.
• Charged particles have potential (stored)
energy, meaning they can do work when
they move.
• The smallest units of electric charge
are:
o Electron – negative charge
o Proton – positive charge
• The fundamental SI unit of electric
charge is the coulomb (C).
Electric Field
• An electric field is the lines of force that
cause charged particles to move.
• It explains how one charge can affect
another without direct contact.
• Electric fields guide the movement of
electrons from one pole to another.
Electrostatics
• Electrostatics is the study of stationary
(non-moving) electric charges.
• It focuses on how electric charges behave
when they are at rest.
Electrostatic Laws
Electrostatics follows several basic laws that
explain how charges interact.
1. Law of Repulsion and Attraction
• Electric fields:
o Radiate outward from a positive
charge
o Move toward a negative charge
• Like charges repel each other (positive–
positive or negative–negative).
• Unlike charges attract each other
(positive–negative).
• Uncharged particles do not produce an
electric field.
• The attraction or repulsion between
charges is caused by the electric field
and is called electrostatic force.
2. Inverse Square Law
• The force between two electric charges:
o Is directly proportional to the
product of their charge
magnitudes.
o Is inversely proportional to the
square of the distance between
them.
• This means:
o Charges closer together have a
stronger force.
o Charges farther apart have a
weaker force.
3. Law of Distribution
• In a solid conductor, electric charges:
o Spread out uniformly on the
surface.
o This happens because like
charges repel each other.
4. Law of Concentration
• Electric charges tend to concentrate:
o Most strongly at sharp or
pointed areas of a surface.
• In x-ray tubes:
o Components are rounded and
highly polished to prevent charge
buildup at sharp points.
5. Law of Movement
• Only negative charges (electrons) are
free to move along solid conductors.
• Positive charges are tightly bound within
the atomic nucleus and do not move.
Electricity (Energy Conversion)
• Electrical energy can be converted into
other forms:
o Chemical → Electrical (battery)
o Electrical → Mechanical (motor)
o Electrical → Thermal (electric
barbecue)
Electrification
• Electrification is the transfer or
movement of electrons from one object
to another.
• It describes how electrons are:
o Added to an object, or
o Removed from an object
• Electrification occurs through three
methods:
o Friction
o Contact
o Induction
1. Friction
• Happens when two objects are rubbed
together.
• Low humidity (cold weather) makes
electron transfer easier.
• Examples:
o Rubbing hands together
o Combing hair
2. Contact
• Occurs when two objects touch, allowing
electrons to move between them.
• Charges become balanced through
simple equalization.