LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER COMPUTER PRESENTATIONS FOR KS3 SCIENCE - PHYSICS ©2003, STEVE PARKER

1 1 KS3 SCIENCE - PHYSICS KS3 SCIENCE - PHYSICS Nature of Electricity Nature of Electricity

WHAT IS ELECTRICITY? 2 2

3 3 A “Charge” is an attraction or repulsion between tiny particles A “Charge” is an attraction or repulsion between tiny particles A charge is either “Positive” or “Negative” A charge is either “Positive” or “Negative”

WHAT IS ELECTRICITY? 4 4 A charge is either “Positive” or “Negative” A charge is either “Positive” or “Negative” You can put a positive charge on a perspex ruler by rubbing it with a woollen cloth You can put a positive charge on a perspex ruler by rubbing it with a woollen cloth You can put a negative charge on a plastic comb by combing your hair You can put a negative charge on a plastic comb by combing your hair

WHAT IS ELECTRICITY? 5 5 A charge is either “Positive” or “Negative” A charge is either “Positive” or “Negative” If you put the ruler and comb together, they will attract each other If you put the ruler and comb together, they will attract each other

WHAT IS ELECTRICITY? 6 6 A charge is either “Positive” or “Negative” A charge is either “Positive” or “Negative” But two rulers will repel each other, as will two combs But two rulers will repel each other, as will two combs

WHAT IS ELECTRICITY? 7 7 Atoms have tiny particles moving around them, called “Electrons” and these carry a negative charge Atoms have tiny particles moving around them, called “Electrons” and these carry a negative charge

WHAT IS ELECTRICITY? 8 8 Atoms have other particles inside them called “Protons”, which carry a positive charge Atoms have other particles inside them called “Protons”, which carry a positive charge

ELECTRIC CURRENT 9 9

10 ELECTRIC CURRENT We call such a pump a “Cell” and several cells are a “Battery” We call such a pump a “Cell” and several cells are a “Battery” -VE +VE An electric “Current” is a flow of charge, which happens when some thing pumps charge around An electric “Current” is a flow of charge, which happens when some thing pumps charge around

-VE +VE 11 An electric “Current” is a flow of charge, which happens when some thing pumps charge around An electric “Current” is a flow of charge, which happens when some thing pumps charge around ELECTRIC CURRENT Negatively charged electrons flow through the wire Negatively charged electrons flow through the wire

-VE +VE 12 Electrons, being negatively charged, are repelled by the -ve terminal and attracted by the +ve one Electrons, being negatively charged, are repelled by the -ve terminal and attracted by the +ve one ELECTRIC CURRENT Electrons move in this direction Electrons move in this direction

-VE +VE 13 But positively charged particles move in the opposite direction, and we say that current flows from the +ve to the -ve terminal But positively charged particles move in the opposite direction, and we say that current flows from the +ve to the -ve terminal ELECTRIC CURRENT Current flows only if there is a complete circuit Current flows only if there is a complete circuit

14 Electric current can produce four types of energy Electric current can produce four types of energy ELECTRIC CURRENT Light Heat Motion Sound

CURRENT & VOLTAGE 15

CURRENT & VOLTAGE 16 The current is the rate at which charge is flowing The current is the rate at which charge is flowing If the current is big, the charge moves quite quickly If the current is big, the charge moves quite quickly

CURRENT & VOLTAGE 17 The current is the rate at which charge is flowing The current is the rate at which charge is flowing If the current is small, the charge moves more slowly If the current is small, the charge moves more slowly If the current is big, the charge moves quite quickly If the current is big, the charge moves quite quickly

CURRENT & VOLTAGE 18 Current is measured in “Amperes”, or “Amps”, which we can measure with an “Ammeter” Current is measured in “Amperes”, or “Amps”, which we can measure with an “Ammeter” A A CELL

CURRENT & VOLTAGE 19 A simple experiment with bulbs in a circuit shows that current is not used up as it flows around - current is the same throughout A simple experiment with bulbs in a circuit shows that current is not used up as it flows around - current is the same throughout AMMETER A A A A CELL BULB

CURRENT & VOLTAGE 20 The cell gives energy to the charged electrons to move them around the circuit - this energy is turned into light when they reach the bulbs The cell gives energy to the charged electrons to move them around the circuit - this energy is turned into light when they reach the bulbs AMMETER A A A A CELL BULB

CURRENT & VOLTAGE 21 The amount of energy given to the charged electrons as they are pumped around is the “Voltage”, measured in “Volts” The amount of energy given to the charged electrons as they are pumped around is the “Voltage”, measured in “Volts” -VE +VE

CURRENT & VOLTAGE 22 The energy depends on the difference in electrical energy between the two terminals, which is known as the “Potential Difference” (p.d.) The energy depends on the difference in electrical energy between the two terminals, which is known as the “Potential Difference” (p.d.) High Energy High Energy Low Energy

CURRENT & VOLTAGE 23 The energy depends on the difference in electrical energy between the two terminals, which is known as the “Potential Difference” (p.d.) The energy depends on the difference in electrical energy between the two terminals, which is known as the “Potential Difference” (p.d.) The bigger the difference, the more energy is given to the electrons The bigger the difference, the more energy is given to the electrons High Energy High Energy Low Energy

CURRENT & VOLTAGE 24 Electricity generated during a storm has extremely high voltages Electricity generated during a storm has extremely high voltages High Energy High Energy Low Energy