CHAPTER 9Static charge – an electric charge that builds up because of an imbalance between the number of electrons and protonsDischarge – to remove all excess static electric charge so that the object is neutralElectrostatics – the study of static electric chargeLaw of Electric Charges – the law that states that opposite electric charges attract, and like electric charges repelInduced Charge Separation – a slight shift in the position of electronsCharging by Friction – transferring an electric charge to another by a rubbing actionCharging by conduction – transferring an electric charge from one object to another by touching the objects togetherCharging by induction – transferring an electric charge from one object to another by bringing a charged object close to, without touching, another objectInsulator – a material in which the electrons are bound tightly to the nucleus and are not free to move to a neighbouring atom; plastic is a good insulatorConductor – a material in which the electrons are free to travel to a neighbouring atom; metals are good conductorsGrounded – connection of an object to Earth through a conductorVan de Graaf generator – a type of static electricity generator that separates large amounts of charge; used to research and demonstrate static electricityElectric force – the force exerted on an object with an electric charge; can be a force of attraction or repulsionCoulomb’s law – the law that states the relationship between electric force, size of charge, and distance; the strength of the electric force increases with increasing electric charges and decreases with increasing distanceCoulomb – a measurement of the quantity of electric charge; the amount of electricity transported by a current of one ampere flowing for one second; one coulomb of charge is 6.28 x 10-18 electrons

CHAPTER 10Current electricity – the controlled flow of electrical charges in a circuitJoule – the SI unit for measuring energy and workBattery – a combination of two or more electric cellsLoad – any device that converts electrical energy into another form of energyCircuit diagram – a diagram that uses a set of standard symbols to represent components in an electric circuitElectric current (I) – a flow of electric charges through an electric circuit; measured in amperes; symbol is IAmpere (A) – SI unit for measuring electric currentConventional current – flow of positive charges in a circuit, which is opposite to the flow of electrons: from the positive terminal of the energy sourceElectron flow – direction that electrons move in an electric circuit: from the negative terminal to the positive terminal of the energy sourceDirect current (DC) – an electric current that flows in one direction only through an electric circuitAlternating current (AC) – an electric current that periodically reverses its directionSeries circuit – circuit in which the components are connected end to end so that the electrical current has only one path to followParallel circuit – a circuit in which each electrical load is connected to the energy source by its own separate paths; the electric current is split among the loadsAmmeter – an instrument that measures electric current in amperes or milliamperesVoltage (V) – the electric potential difference between two points in an electric circuit; measurement of the energy that would be required to move a unit of electric charge from one point to another; measured in volts; symbols = V

Voltmeter – an instrument that measures voltage (electric potential difference) in voltsResistor – an electrical device designed to resist the flow of electrical current in a circuit; a load in a circuit that converts electrical energy to another form of energyOhm ( ) – the SI unit for measuring resistanceΩResistance (R) – a measurement of the opposition to the flow of electric current through a circuit; measured in ohms; symbol = ROhm’s law – the law that defines the relationship between voltage, current, and resistance; voltage varies directly with current

CHAPTER 11Work (W) – a measurement of the amount of energy transformed from one form of energy (such as electrical energy) into another form of energy (such as light energy); measured in joules; symbol is WEnergy (E) – the ability of an object to do work; exists in many forms including electrical energy, light energy, and nuclear energy; measured in joules; the symbol is EPotential Energy (PE) – energy stored by an object as a result of its position relative to the ground (gravitational potential energy), its shape (elastic potential energy), or its condition (chemical potential energy) rather than its motion; measured in joulesKinetic Energy (KE) – energy that an object has because of its motion; measured in joules; its symbol is KELaw of Conservation of Energy – the law that states that when energy changes from one for to another; no energy is lostPower (p) – the rate of doing work or transforming energy; measured in wattsWatt (W) – SI unit for measuring powerKillowatt • hour (kW • h) – SI unit for measuring energy usage; the use of one kilowatt of power for one hour

Protons: have a positive charge and a large mass 9about 2000 times larger than an electron)Electrons: have a negative charge and a very tiny massNeutrons: have no charge and are similar in mass to a protonProtons and neutrons are in the nucleus of an atom and do not move from the nucleus when an atom becomes charged. Electrons move around the outside of the nucleus and can be more easily added or removed from an atom.

Charging by friction – eg. Large amounts of electric charge build up on clothes to be transferred from one object to another.Charging by conduction – eg. If you walk across a carpet and get a spark by touching a metal doorknob, you are transferring some of your charge to the doorknob by conduction.Charging by induction – eg. Buildup of dust on the screen of a television or computer monitor. When a screen is turned on, it begins to build up a charge. When a neutral dust particle comes near the screen, the screen induces an opposite charge on the near side of the dust particle and a similar charge on the far side. The dust is attracted to the screen.

ELECTROSCOPE – When a positively charged strip is brought near the electroscope, it induces a separation of charge. The ball on the top of the electroscope becomes negatively charged and the two leaves become positively charged. Since the two leaves have the same charge, they repel each other and spread out. When the charged object is taken away, there is no longer an induced separation of charge and the leaves return to their original position.

LIGHTNING – Clouds contain millions of water droplets that collide with other droplets as they rise and fall. During these collisions, electrons are transferred from the rising water droplets to the falling water droplets. The negatively charged water droplets collect in the lower part of the cloud, giving it a negative charge. The positively charged water droplets continue to rise, carrying the positive charge to the top of the cloud. This causes the cloud to acquire a separation of charge. As the

collissions between droplets continue to occur, and the charges at the top and bottom of the cloud increase, the separation of charge in the cloud becomes more intense. Eventually, the electrons at the surface are repelled by the strong negative charge at the lower part of the cloud. This causes Earth’s surface to acquire a strong positive charge.

CHAPTER 9Static electric charges can build up on objects.• A static electric charge remains at rest until it is discharged.• A neutral object has an equal number of positive and negative charges.• Neutral objects can be given static charges that are either negative (by gaining electrons) or positive (by losing electrons).• Neutral objects are attracted to charged objects because of separation of charges.

Objects become charged by friction, conduction, and induction.• Friction causes one object to gain electrons from another object.• Some materials, such as metals, are conductors of electricity, while other materials are insulators.• An object is charged by conduction when the excess charge on one objectis transferred through contact to another object.• Induction occurs when a charged object influences the charge distributionin another object.

An electric force between static charges can either attract or repelthe charges.• Like charges repel each other, and opposite charges attract each other.• The size of the electric force between two charged objects increases with the sizes of the charges on the objects and decreases as the distance between the objects increases.

The discharge of static electricity in the form of lightning can bedangerous, but static electricity also has useful applications.• Lightning is a spectacular example of static electric discharge.• A metal-leaf electroscope is a device that can be given a known charge to determine the type and size of charge on an object.• A Van de Graaff generator is a device that separates large quantities of static charge.• Laser printers and electrostatic precipitators apply the principles ofstatic electricity.

CHAPTER 10In a circuit, electric charges flow from an energy source to a device that uses the energy.• The components in a circuit can be represented using circuit diagram symbols.• An electric cell is an energy source. A battery is a combination of two or more electric cells.• Conventional current is the flow of positive charge. Electron flow is the flow of negative charge and goes from the negative terminal and returns to the positive terminal of a battery in a circuit.• Circuits may contain resistors that are in series or in parallel.

Current and voltage in a circuit can be measured by meters.• Electric current is the rate of flow of electric charge and is measured inamperes by ammeters placed in series.• Voltage (electric potential difference) is the amount of energy per coulomb of charge and is measured in volts by voltmeters placed in parallel.• When electric cells are added in series, the voltage increases.• When electric cells are added in parallel, the voltage does not change.

Ohm’s law relates resistance, voltage, and current in a circuit.

• A resistor resists the flow of electric current and, thus, has resistance.• Ohm’s law states that the resistance of a material is equal to the ratio of voltage divided by current.• The equation for Ohm’s law is R = V/I or V=IR

Series and parallel circuits differ in terms of current, voltage, andtotal resistance.• In a series circuit, the current remains the same, but the voltage changes.• In a parallel circuit, the current changes, but the voltage remains the same.• The total resistance of a circuit depends on the number of individualresistances.• Increasing the number of resistors in series increases the total resistance.• Increasing the number of resistors in parallel decreases the total resistance.

CHAPTER 11Electrical energy is a type of energy that can be converted into other types of energy.• Electrical energy can be potential energy, such as the energy stored in a battery, or it can be the energy of moving electrons in an electric current that can do work.• Potential energy is energy that can be stored. Kinetic energy is the energy that is associated with motion.• Work is done when energy is transformed. Energy is defined as the ability to do work. The metric unit for both work and energy is the joule (J).• Energy comes in many types and is often only observed when it changes from one type to another. Energy is always conserved.• We can use various equations to calculate the electrical energy of a device.

Electrical power is the rate of transforming electrical energy intoanother type of energy.• Power is the rate of doing work or the rate of transforming energy.The metric unit for power is the watt (W).• We can use various equations to calculate the electrical power of a device.

Electrical energy is produced from renewable and non-renewable resources.• Electricity can be generated from renewable resources including water (hydro), the Sun (solar), wind, biomass, tides, geothermal, and landfill gas.• Electricity can be generated from non-renewable resources, including fossil fuels and nuclear reactions.

Energy consumption can be determined given the power rating of a device and the duration of use.• Electrical energy is often measured in kilowatt•hours (kW•h).• Household electrical energy is sold in units of kilowatt•hours (kW•h), not joules, and is measured by kilowatt•hour meters (electric meters).• EnerGuide labels provide information about the energy consumption and efficiency of appliances in Canada.