Partial Notes on Radiologic Physics 2Radiation Physics | Hariette A.W. | April 13, 2009 at 17:41
ELECTRICITY AND MAGNETISM
- has mass and energy equivalence and may also have electric charges
- Electrically neutral which means, in the entire universe the total number of positive charge is equal to the total number of negative charge.
- derived from the word electricity
- Can be created by contact, friction and induction
- Due to the movement of negative electric charges.
• The primary function of x-ray tube is to convert electric energy to EMR or x-rays.
Two Studies of Electric Charges
- Electrostatics- the study of electric charges in stationary form.
- Electrodynamics- the study of electric charges in motion.
Four Fundamental Properties of Matter
- Energy equivalence
- Electric charge
2 Units of Electric Charges
- electrons- the smallest unit of electric charge.
- proton- positively charge particle.
● Earth- huge reservoir for stray electric charge.
Four Electrostatics Law
- Unlike charges attract, like charges repel.
● Electrostatic Force- the force of attraction between unlike charges or repulsion between like charges which is due to the electric field.
2. Coulombs’ Law- states that electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the distance between them.
3. Electric Charge Distribution- states that electric charge distribution is uniform through out or on the surface.
4. Electric Charge Concentration- states that electric charges are concentrated along the sharpest curvature of the surface.
- Is also known as electricity
Electric Current - the flow of electron and occurs in many types of objects.
Conductors and Insulators
- Conductor- is a substance through which e- flow easily
- Insulator- any material that does not allow the flow of e- or inhibits the flow of electrons
- possesses two properties of a conductor and insulator.
- the property of the material to exhibits no resistance below a critical temperature.
Four Electric States of Matter
- Superconductors- possesses no resistance to electron flow (niobium and titanium)
- Conductor- it obeys Ohms’ Law and requires a voltage (copper and aluminum)
- Semi-conductor- can be conductive and can be resistive (silicon and germanium)
- Insulators- do not permit e- flow (glass and rubber)
● 1 ampere= 1 flow of e-/sec