This document is a lecture on electromagnetism covering key historical figures and concepts, such as the relationship between electricity and magnetism, electric motors, and electromagnets. It discusses applications of electromagnetic radiation, including communication systems, medical imaging, and motors in various devices. The lecture emphasizes the fundamental principles of electric and magnetic fields and their interaction, alongside practical examples of their use in technology.

1. Duration: 60 min DPT Medical Physics Lecture 05
Electromagnetism
Instructor:
Engr. Taimoor Muzaffar Gondal
taimoor.muzaffar@superior.edu.pk
Lecture 05

2. Duration: 60 min DPT Medical Physics Lecture 05
A Brief History
1600 William Gilbert, On magnetism; magnetic materials; poles that attract & repel; Earth’s
magnetic field, compass ‘dip’
1820 Hans Christian Oersted finds that an electric current deflects a compass needle.
1820 Andre Marie Ampère finds that parallel wires carrying current produce forces on each other.
1820s, 1830s Michael Faraday develops the concept of electric field and shows that
electric current + magnetism -> motion (motor effect)
motion + magnetism -> electric current (electromagnetic induction)
1860s James Clerk Maxwell (1831-1879) established a mathematical description of
electromagnetism.

3. Duration: 60 min DPT Medical Physics Lecture 05
Magnetic fields from electricity
A static distribution of charges produces an
electric field
Charges in motion (an electrical current) produce
a magnetic field
electric current is an example of charges
(electrons) in motion

4. Duration: 60 min DPT Medical Physics Lecture 05
Magnetic Effect of a Current
 An iron rod placed inside a coil of wire has increased magnetic field when
the current is switched on
 When the current is switched off, the iron loses its magnetism
 The set-up is known as an electromagnet
 Used in many applications
 Gives a magnetic field that can be switched on and off. when desired

5. Duration: 60 min DPT Medical Physics Lecture 05
Electromagnets
Arranging wire in a coil and running a current through produces a magnetic field that looks
a lot like a bar magnet
called an electromagnet
putting a real magnet inside, can shove the magnet back and forth depending on current
direction: called a solenoid

6. Duration: 60 min DPT Medical Physics Lecture 05
 The next part of the story is that a changing magnetic field produces an
electric current in a loop surrounding the field
 called electromagnetic induction, or Faraday’s Law
Induced Current

7. Duration: 60 min DPT Medical Physics Lecture 05
The Electromagnetic Connection
 A changing magnetic field produces an electric field, and a changing
electric field produces a magnetic field.
 Electric and Magnetic fields can produce forces on charges
 An accelerating charge produces electromagnetic waves (radiation)
 Both electric and magnetic fields can transport energy
 Electric field energy used in electrical circuits, e.g., released in
lightning
 Magnetic field carries energy through transformer, for example

8. Duration: 60 min DPT Medical Physics Lecture 05
What’s “Waving” in EM waves?
What medium transports sound waves? (Air)
 Can there be sound waves in the vacuum of outer space? (No)
 What medium transports water waves? (Ocean Water)
 What medium transports radio waves? (No medium)
 A topic of considerable debate in the late 1800’s and early 1900’s
 Led to the concept of the “aluminiferous ether” – an invisible “jello” that
was thought to vibrate electromagnetically
 Experiments that sought this ether didn’t find it!
 This was quite a surprise

9. Duration: 60 min DPT Medical Physics Lecture 05
Examples of Electromagnetic Radiation
 AM and FM radio waves (including TV signals)
 Cell phone communication links
 Microwaves
 Infrared radiation
 Light
 X-rays
 Gamma rays
 What distinguishes these from one another?

10. Duration: 60 min DPT Medical Physics Lecture 05
Uses of Electromagnetic Waves
 Communication systems
 One-way and two-way
 Radar
 Cooking (with microwaves)
 Medical Imaging (X rays)
 “Night Vision” (infrared)
 Astronomy (radio, wave, IR, visible, UV, gamma)
All that we experience through our eyes is conveyed by
electromagnetic radiation…

11. Duration: 60 min DPT Medical Physics Lecture 05
What are some uses for electric magnets?
 Electromagnets are useful for lifting and moving large metal objects
containing iron. When current runs through the solenoid coils, it creates a
magnetic field that attracts the metal objects. Turning off the current turns off
the magnetic field so that the metal can be easily dropped in a new place.
 Powerful electromagnets can raise a maglev train above its track. Just as
poles of a bar magnet repel each other, electromagnets in the train and track
repel each other when the electric current is turned on.

12. Duration: 60 min DPT Medical Physics Lecture 05
What are some uses for electric magnets?
 A galvanometer is a meter that measures the strength and direction of an electric
current in a wire.
 A galvanometer contains an electromagnet between the poles of a permanent
magnet. When current is applied to the electromagnet, the two magnetic fields
interact and cause the electromagnet to turn.
 The indicator, attached to the electromagnet, moves to one side of the zero on
the scale, indicting the strength and direction of the current.

13. Duration: 60 min DPT Medical Physics Lecture 05
Magnetic resonance imaging (MRI) machines use
powerful electromagnets and radio waves to produce
detailed images of the body’s interior.
Doctors use MRI scans to diagnose many conditions,
including broken bones and strained tendons.
Some MRI scans help scientists understand how the
brain works.
A Look Inside

14. Duration: 60 min DPT Medical Physics Lecture 05
How do motors work?
 An electric motor changes electrical energy into mechanical
energy.
 Electric motors range in size from large motors, used to
power Ferris wheels, to small motors used in computer
cooling fans. Almost every time a device uses electricity to
make something move, there is a motor involved.

15. Duration: 60 min DPT Medical Physics Lecture 05
Motors everywhere
 lifts & escalators; fans, turbines, drills; wheelchairs; car windscreen wipers, starter
motors, windows & side mirrors; motors in electric cars, locomotives & conveyor
belts; industrial robots, saws and blades in cutting and slicing processes; food mixers
& blenders, microwave ovens; hand power tools such as drills, sanders, routers;
electric toothbrushes, shavers, hairdryers; vacuum cleaners, sound systems,
computers …
 using electricity supplied by power station generators

16. Duration: 60 min DPT Medical Physics Lecture 05
Simple DC motor

17. Duration: 60 min DPT Medical Physics Lecture 05
Simple DC motor

18. Duration: 60 min DPT Medical Physics Lecture 05
End of Lecture 05
For any kind of queries and questions you are advised to
write at
taimoor.muzaffar@superior.edu.pk
Or visit my office during consulting hours
This lectures can also be downloaded from
https://www.slideshare.net/Taimoor_Gondal