# Chapter 7 Section 1 Electric Charge

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Chapter 7 Section 1 Electric Charge
Electricity Chapter 7 Section 1 Electric Charge

Sections 1. Electric Charge slides 3 - 35
2. Electric Current slides 3. Electrical Energy slides

Electric Charge The center of an atom is made of protons (+) and neutrons (no charge).

Electric Charge The center of an atom is made of protons (+) and neutrons (no charge). Electrons (-) move around the center of the atom.

Electric Charge The amount of + Charge on a proton = The amount of –
Charge on an electron.

Electric Charge The amount of + Charge on a proton = The amount of –
Charge on an electron. Each atom has the same number of protons & electrons making them electrically neutral.

Electricity Atoms have no charge.

Electricity Atoms have no charge. - ion if it gains electrons

Electricity Atoms have no charge. - ion if it gains electrons
+ ion if it loses electrons

Electricity Atoms have no charge. - ion if it gains electrons
+ ion if it loses electrons Electrons can move from atom to atom or from object to object.

Static Electricity Is the buildup of charges on an object.

Static Electricity Is the buildup of charges on an object.
When there is static electricity, the electric charges are not balanced.

Static Electricity Is the buildup of charges on an object.
When there is static electricity, the electric charges are not balanced. The Law of Conservation of charge states that charge can be transferred from object to object but it cannot be created or destroyed.

Electricity Opposite charges attract Like charges repel + - + + - -

Electricity The electric force between charged objects depends on how far apart they are.

Electricity The electric force between charged objects depends on how far apart they are. The force decreases the farther apart the charges are.

Electricity The electric force between charged objects depends on how far apart they are. The force decreases the farther apart the charges are. The electric force also depends upon the amount of charge on the objects.

Electricity The electric force between charged objects depends on how far apart they are. The force decreases the farther apart the charges are. The electric force also depends upon the amount of charge on the objects. More charge = More force

Electric Field Area around every electric charge that exerts a force.
Movement of a positive charge in electric fields. + -

Electric & Gravitational Force
Electric forces are stronger than gravity.

Electric & Gravitational Force
Electric forces are stronger than gravity. Atoms are held together by electric forces.

Electric & Gravitational Force
Electric forces are stronger than gravity. Atoms are held together by electric forces. These forces cause chemical bonds to make a new substance.

Electric & Gravitational Force
Electric forces are stronger than gravity. Atoms are held together by electric forces. These forces cause chemical bonds to make a new substance. Electric forces between atoms are greater than the gravitational forces between atoms.

Electric & Gravitational Force
Electric forces are stronger than gravity. Atoms are held together by electric forces. These forces cause chemical bonds to make a new substance. Electric forces between atoms are greater than the gravitational forces between atoms. Electric forces between most objects are less than the gravitational forces between them because most objects are elec. neutral.

Conductors & Insulators
Electrons move more easily in conductors.

Conductors & Insulators
Electrons move more easily in conductors. Ex. Metals such as copper Insulators do not allow electrons to move as easily. Ex. Plastic, wood rubber and glass

Charging Objects Charging by contact- transferring charges by touching or rubbing ex. Clothes in a dryer

Charging Objects Charging by contact- transferring charges by touching or rubbing ex. Clothes in a dryer Charging by induction- charged object rearranges the electrons on a nearby neutral object.

Lightning Large static discharge between clouds and the ground that causes atoms & molecules to light up.

Lightning Large static discharge between clouds and the ground that causes atoms & molecules to light up. Thunder- Electric energy in a lightning bolt rips electrons off atoms in the air causing great amounts of heat, up to 25,000 °C.

Lightning Large static discharge between clouds and the ground that causes atoms & molecules to light up. Thunder- Electric energy in a lightning bolt rips electrons off atoms in the air causing great amounts of heat, up to 25,000 °C. The heat makes the air around the lightning bolt move faster creating sound waves.

Grounding Grounding avoids damage by providing a path for electric charge to move to earth.

Electroscope Can detect when an object has an electric charge.
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Electroscope Can detect when an object has an electric charge.
The metal rod is a conductor.

Electroscope Can detect when an object has an electric charge.
The metal rod is a conductor. When the leaves have a charge they repel each other and spread apart.

Electric Current Chp 7 Section 2

Electric Current The net movement of electric charges in one direction.

Electric Current The net movement of electric charges in one direction. Measured in units called amperes or amps.

Electric Current The net movement of electric charges in one direction. Measured in units called amperes or amps. Symbol for amperes is A.

Electric Current The net movement of electric charges in one direction. Measured in units called amperes or amps. Symbol for amperes is A. Measures the electrons that flow past one point.

Electric Current The net movement of electric charges in one direction. Measured in units called amperes or amps. Symbol for amperes is A. Measures the electrons that flow past one point. 1 A = 6,250 million billion electrons moving past a point every second.

Voltage The electric force that makes charges move.

Voltage The electric force that makes charges move.
Voltage is like the force that acts on water in a pipe.

Voltage The electric force that makes charges move.
Voltage is like the force that acts on water in a pipe. Water flows from higher pressure to lower; likewise, electric charge flows from higher voltage to lower voltage.

Voltage difference Related to the force that makes electric charges flow.

Voltage difference Related to the force that makes electric charges flow. Measured in units called volts (V).

Electric Circuit Closed loop-like path that current must follow.
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Electric Circuit Closed loop-like path that current must follow.
If the circuit is broken, current will not flow & bulb will not light.

Batteries Provide the voltage difference that keeps electric current flowing in a circuit.

Batteries Provide the voltage difference that keeps electric current flowing in a circuit. The positive & negative ends are called terminals.

Batteries Provide the voltage difference that keeps electric current flowing in a circuit. The positive & negative ends are called terminals. When a closed path connects the terminals, current will flow.

Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution A. dry cell - use paste – flashlight battery B. wet cell – use liquid – car battery

Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution A. dry cell - use paste – flashlight battery B. wet cell – use liquid – car battery Photovoltaic – electrons move when light hits a material – calculators, solar panels

Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution A. dry cell - use paste – flashlight battery B. wet cell – use liquid – car battery Photovoltaic – electrons move when light hits a material – calculators, solar panels Thermoelectric – electrons move across two metals joined together & held at different temperatures – thermostats for ovens

Types of Electric Cells
Electrochemical- electrons move b/w different metals in an electrolyte solution A. dry cell - use paste – flashlight battery B. wet cell – use liquid – car battery Photovoltaic – electrons move when light hits a material – calculators, solar panels Thermoelectric – electrons move across two metals joined together & held at different temperatures – thermostats for ovens Piezoelectric – electrons move when opposite surfaces of crystals become charged under pressure – mikes, keyboards

Electrical outlets Also give a voltage difference, usually higher than a battery, such as 120 V or 240 V for large appliances.

Resistance The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light

Resistance The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light. Electrons flowing through the wire filament of a light bulb bump into metal atoms heating the filament until it glows lighting up…electric to thermal to radiant energy.

Resistance The tendency for a material to oppose the flow of electrons, changing electric energy into heat and light. Electrons flowing through the wire filament of a light bulb bump into metal atoms heating the filament until it glows lighting up. Resistance turns electric energy into heat & light.

Resistance is measured in units called ohms (Ω) or the Greek letter omega.

Resistance is measured in units called ohms (Ω) or the Greek letter omega. Temperature, length, & thickness of a material can affect its electrical resistance.

Resistance is measured in units called ohms (Ω) or the Greek letter omega. Temperature, length, & thickness of a material can affect its electrical resistance. Hotter, longer & thinner – more Ω

a simple circuit requires
1. Source of voltage difference i.e. Battery 2. Device with resistance i.e. light bulb 3. Conductors i.e. wires connecting all three so that current can flow.

Ohm’s law States that the current in a circuit equals the voltage difference divided by the resistance.

Ohm’s law States that the current in a circuit equals the voltage difference divided by the resistance. If I stands for electric current, Ohm’s law can be written as : current (in amps) = voltage difference resistance (in Ω) I = V/ R or R = V/I

Problem Suppose a current of 0.5 A flows in a 75-W light bulb. The voltage difference b/w the ends of the filament is 120 V. Find the resistance of the filament.

Problem Suppose a current of 0.5 A flows in a 75-W light bulb. The voltage difference b/w the ends of the filament is 120 V. Find the resistance of the filament. R = V/I = 120/0.5 = 240 The resistance is 240 Ω.

Electrical Energy Chapter 7 section 3

Electrical energy When you turn a hair dryer on, you close a circuit. EE turns into thermal energy & ME. Voltage difference – Resistance – Conductor -

Electrical energy When you turn a hair dryer on, you close a circuit. EE turns into thermal energy & ME. Voltage difference – outlet Resistance – hair dryer Conductor - wires

Kinds of Circuits Series – Parallel -

Kinds of Circuits Series – current has only one loop to flow through i.e. flashlights Parallel -

Kinds of Circuits Series – current has only one loop to flow through i.e. flashlights, some Christmas lights Parallel – have at least two circuits for current to move through i.e. houses

Circuits <target.raf.mod.uk > <

Circuits SERIES PARALLEL

Parallel Circuits Break up current lowering resistance.

Parallel Circuits Break up current lowering resistance.
More current flows through paths with less resistance.

Parallel Circuits Break up current lowering resistance.
More current flows through paths with less resistance. Houses, cars and most electrical systems use parallel systems.

Household Circuits

Household Circuits There is a main switch & a circuit breaker or fuse box.

Household Circuits There is a main switch & a circuit breaker or fuse box. Parallel circuits branch out from the circuit breaker or fuse box.

Household Circuits There is a main switch & a circuit breaker or fuse box. Parallel circuits branch out from the circuit breaker or fuse box. The circuits run to wall outlets, appliances, & lights.

Fuses Many appliances use current from the same circuit causing more heat in the wires.

Fuses Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker.

Fuses Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker. A fuse is a small glass tube with a piece of metal inside that melts if the current is too high breaking the circuit.

Fuses Many appliances use current from the same circuit causing more heat in the wires. To keep wires from causing a fire, household circuit include a fuse or circuit breaker. A fuse is a small glass tube with a piece of metal inside that melts if the current is too high breaking the circuit. To restore current, the fuse must be replaced.

Fuses Using too many appliances at once is the main cause for a blown fuse. You should turn off or unplug some appliances before changing the fuse.

Circuit Breaker Switching device that prevents circuits from overheating by opening the circuit if the current is too high.

Circuit Breaker Switching device that prevents circuits from overheating by opening the circuit if the current is too high. You can reset the breaker by flipping the breaker box back to its original position but you should turn off or unplug some of the appliances first.

Electric Power Rate at which electrical energy is changed into another form of energy.

Electric Power Rate at which electrical energy is changed into another form of energy. Different appliances use different amounts of energy and are usually marked with a power rating.

Electric Power Rate at which electrical energy is changed into another form of energy. Different appliances use different amounts of energy and are usually marked with a power rating. Electric power (watts) = current (amps) X voltage difference (V) or P = IV Power is usually measured in kilowatts (kW)

Electric energy calculation
Electrical energy (kW) = electric power (kW) X time (hours) or E = Pt A 100 W light bulb left on for 5 h uses: E = Pt = (0.1kW) (5h) = 0.5 kWh If the power company charges 10 cents per kW, the cost of using the light would be 5 cents.

Cost of using Home Appliances
Hair dryer Stereo Color TV Power rating 1, Hours/day Kwh /month Cost / kWh \$0.09 \$0.09 \$0.09 Monthly cost \$0.68 \$0.54 \$2.16

Electric Fuse Circuit Breaker contains contains that that when when And makes the current

A piece of metal Electric Fuse Circuit Breaker contains contains that
Switches the circuit off Can melt when when It gets too hot And makes the current STOP