ELECTRICITY AND MAGNETISM

A JOURNEY TOWARDS THE SMALLEST PART OF MATTER

TOPICS

• Electric fields and magnetic field• The presence of magnetic field in current carrying wire.

OBJECTIVES:

• Explain the behavior of charges in the electric field. • State that a magnetic field exists around a current carrying wire.• Explain how electricity is related to magnetism and the nature of magnetic

field.

ACTIVITY Group ActivityGroup 1 Charge HockeyGroup 2 Magnetic FieldGroup 3 Magnetic fieldGroup 4 Magnetic fieldGroup 5 Charge Hockey

EM Induction

Magnetic Field (B)

Magnetism

B due to I

Force of B on I

ElectromagnetsMotors

Faraday’s Law

•Generator/Transformer•Power Transmission

• Magnetic Field• Magnetic forces

• Electrical Power• Electrical energy

Electric circuit/connection

Ohm’s Law

Electric Charge

Electric Force

Electric Field

Electric Potential

WORLD OF ELECTRICITY AND MAGNETISM

Electric Current (I)

Electrostatics

Magnetic Field and Current

• Positive and negative electric charges• Attraction/Repulsion between charges

Electric currentElectric circuits (at home)

• Involves…Electric charges

The forces between them and their behavior in materials

Electrostatics

THE CHARGES…•Everything is made of atoms which contain POSITIVE particles called PROTONS and NEGATIVE particles called ELECTRONS.

Proton (+)

Neutron

Electron (-)

•An atom will usually have the same number of positives and negatives•This makes the atom NEUTRAL.

Proton (+)

Neutron

Electron (-)

WHAT IS INSIDE AN ATOM?

Thomson’s Plum pudding model

Rutherford model

Rutherford Bohr model

Charge cloud modelQuantum model of the nucleus

ELECTRICAL CHARGE

• Electric charge is given the symbol

qElectrons are the charge carriers that flow in an electrical circuit –from the negative to positive terminals.

ELECTRICAL CHARGE

• Charge is measured in

Coulombs• which is given the symbol

C

ELECTRICAL CHARGE

• The charge on a proton is

1.6 x 10-19C• which is the same size as the charge on an electron.

FUNDAMENTAL RULE OF THE BASE OF ALL ELECTRICAL PHENOMENALike charges repel;

Opposite charges attract.

Source; Paul Hewitt, (1998). Conceptual physics, CA: Saunders Publishing

CHARGING PROCESS

• Charging by friction and contact

• Charging by induction• Charge polarization

ELECTRIC FIELDS AND POTENTIALS

ELECTRIC FIELDThe space around every electric charge is filled with an electric field-a kind of aura that extends through space.

ELECTRIC POTENTIALS

Electric Potentials (volt): work done per unit charge (Bringing a very small positive charge from one point to the other.)

1volt = 1

JOULE COULOMB

POTENTIAL DIFFERENCE OR VOLTAGE (V)

A 9 V battery will give how much energyto each coulomb of charge passingthrough the battery?

9 J

POTENTIAL DIFFERENCE OR VOLTAGE (V)

A 1.5 V battery will give how much energyto each coulomb of charge passingthrough the battery?

1.5 J

POTENTIAL DIFFERENCE OR VOLTAGE (V)

A battery with a p.d. of 6V will give howmuch energy to each coulomb of chargepassing through the battery?

6 J

VOLTAGE OR P.D.

Voltage (or p.d.) is measured in

voltsand is given the symbol

V

WHAT IS ELECTRIC CURRENT?movement of charge round a circuit.

We call this electric current.

ELECTRIC CURRENT: FLOW OF CHARGE

tqI

SI Unit; 1 C/s = 1 ampere, AAfter the French mathematician Andre-Marie Ampere

CHARGE, CURRENT & TIME

•If current is charge flowing per second then

tQI

time in seconds (s)

Current in Amps (A)

Charge transferred in coulombs (C)

so a current of 1 A is 1 C of charge transferred in 1 s.

BASIC CIRCUITS

• Source• Switch• Conductor wire• Load (Bulb)

Why can a bird sit safely on thishigh voltage power line?

What will happen if the bird spreads its wings and touches the pylon?

SUMMARY OF UNITSQuantity Symbol Units Symbolcharge Q coulombs Ctime t seconds scurrent I amperes Avoltage V volts V

Magnets in Electricity

A magnetic field is the region around amagnet in which a magnetic force can bedetected.

A moving charge (electric current) produces magnetic fieldHans Christian Oersted

IT CAME FROM…• Moving/ spinning electron.• It is due to the distortion in

the electric field caused by the motion (Einstein, 1905, Theory of special relativity).

• Every moving/spinning electron is a tiny magnet.

WE CALL IT ELECTROMAGNET

• When magnetic field is produced in the current-carrying wire.

APPLICATIONS ARE…

THANK YOU

I can do all things through Christ which strengthen me.Philippians 4:13

To God be the Glory

REFERENCES

• Murphy & Smooth, (1998). Physics principles and problems, Toronto, Canada: Charles E. Merill Publishing Co.

• Eby & Horton, (1986). Physical science, New York: Macmillan Publishing Company

• Jones & Childers, (1992). Contemporary college physics, 2ndEd, California: Addison-Wesley Publishing Company

• Paul Hewitt, (1998). Conceptual physics, CA: Saunders Publishing