What is it? Electricity is created inside the atom. Each substance is made up of atoms. Atoms contain a nucleus which is made up of protons and neutrons.
On the exterior of the nucleus are the electrons. These electrons move around in an orbit around the nucleus.
Electrons can move from one atom to another. When one electron jumps from one to another, another electron must move. When electrons move quickly from one atom to another, the result is electricity!!
Charges?? All object possess an electrical charge. A charge can either be positive or negative depending on the quantity of protrons and electrons. Remember that all electrons possess a negative charge! + -
Charges?? - + Protons are in the nucleus and have a positive charge. Atoms having more electrons than protons will have _________ charge. - - + - - + + - NEGATIVE - - - -
Charges?? - + + - + Atoms that possess more protons than electrons will have a ______ charge. • Determine the charge on these two atoms. 10 electrons 2 electrons 5 protons 5 protons + + + - POSITIVE - NEGATIVE POSITIVE
The law of attraction and repulsion
attract. Two objects with opposite charges will Two objects with the same charges will repel.
Opposite charges will attract + - Like charges will repel + + - -
Static Electricity Static electricity is a charge that stays on the surface of an object. The electrons move between the objects when they come in contact with one another.
Static electricity - • Before rubbing the balloon in your hair, the two objects (your body and the balloon) are neutral (the quantity of protons are equal to the number of electrons. ) • After rubbing the balloon in your hair, the electrons move from your hair to the balloon. + - + + + - -
Static electricity - + - - Remember!! PROTONS do not move!!! • Your hair looses their electrons and the hair has a POSITIVE CHARGE. + - + + +
+ - + - + - - +
Static electricity + + + + + + • Each strand is now POSITIVE. Like charges push themselves apart and so that each strand now separates itself from one another.
+ - - + + - + -
Insulators and Conductors - What are they?
Conductorrs • A conductor is a material that allows electric currant to travel easily through it. • Metals are good conductors. • Examples: copper,gold,aluminum, brass,silver,stainless steel.
Conductors Conductors allow electrical currents to travel easilybecause there is a lot of space for the electrons to move.
Insulators • An insulator is a material that does not allow electrical currants to travel easily through it. • Examples: plastic, rubber, glass, wood.
Insulators Insulators block the electrons so they they have difficulty traveling through the material.
Staticelectricity and winter • Cold air becomes much drier in winter. • There are less molecules of water in the air during winter. • This aggravates the problem of static electricity.
Dry air is an insulator, so it does not attract negative charges in our body. • Normal air is a weak conductor, so a lot of our negative charges are attracted to the air during the other seasons.
During winter, static electricity accumulates on our clothes and on painted and polished surfaces. • Electrons wait until they find a source of protons, and then ZAP!!!
Three ways to accumulate an electrical charge • Charging by friction • Charging by contact • Charging by induction
Let’s have a look!! FLASH!!
The conductivity of solids copper wood silver the Earth cotton metal salt water rubber pure water the human body SUPER CONDUCTORS SEMI INSOLATORS CONDUCTORS CONDUCTORS Insulators Very difficult for electrons to travel high resistance Conductors Electrons can travel easily high conductivity
Electrostatic substances • Substances which become easily charged • POSITIVE ~ Objects which loosetheir electrons ~ glass, wool, cat hair, human hair, silk
Electrostatic substances • NEGATIVE ~Objects whichgainelectrons ~ platinum, gold, rubber, plastique
The principal of conservation of charge • Electrons can neither be created nor destroyed. • Electrons can move when two objects are in contact but the original number of electrons alwaysstays constant.
Charge it! - Read page 298 - 299 from textbook.
Charging objects by FRICTION • When two objects enter in contact many times (friction), the electronsleaveone object and enter another. A B
Charging objects by FRICTION • Object A acquiers a charge • Object B acquiers a charge Ex: Balloon/comb in your hair NEGATIVE POSITIVE
+ - + - + - - +
The two objects were not already charged but now become charged during the process. • The two objects possess opposite charges in the end, as the electrons left one object and went to the other.
List of electrostatic substances • Acetate • Glass • Wool • Cat hair, human hair • Calcium, magnesium, lead • Silk • Aluminum, zinc • Cotton • Wax • Ebony • Plastic • Carbon, copper, nickel • Rubber • Sulphur • Platinum, gold Gives away it’s electrons easily (Positive charge) Increasing tendancy to gain electrons Electrons shared with great difficulty (negative charge)
Reflection questions • A silk shirt and a pair of wool socks are placed in a dryer. What type of electrical charge will the silk shirt have after being rub with the wool socks? Explain your answer. • What are the best types of brushes to use in winter: plastic or aluminum? Support your answers.
Charging objects by Contact
Lab demonstration – what is happening?
Charging objects by CONDUCTION (contact) • If an object which is already chargedTOUCHES a conductor, the electrons will be transfered between the two objects. Ex: your body and the door knob
Conduction ~ Negativecharge Negative charge NEUTRAL Negative charge Conductor: carries a negative charge, which means there are more electrons in the conductor than in the object. When the conductor touches the object, the electrons will leave the conductor and enter the object. In the end, the object will have a negative charge
Conduction ~ Positive charge + NEUTRAL + Conductor: carries a positive charge, which means there are less electrons in the conductor than the object. When the conductor touches the object, the electrons will leave the object and will enter the conductor. In the end, the object will have apositive charge.
Conduction After Before During
Conduction At the end of conduction, the two objects have the same charge.
Why do we feel a shock when we walk across carpet? When you walk across the carpet, the electrons leave the carpet and attach to your body. Now your body has extra electrons. When you touch a doorknob, the electrons transfer to the knob. ZAP! You feel a discharge of electrons!!