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CHAPTER 1 ELECTRICITY

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ELECTRIC CHARGE Charges Exert Force Atoms are composed of particles with ______. The law of electric charges states that like charges _____and opposite charges _______

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THE FORCE BETWEEN PROTONS AND ELECTRONS Protons and electrons have ________ charges, they are ________ to each other

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THE ELECTRIC FORCE AND THE ELECTRIC FIELD _____________ the force of attraction or repulsion on a charged particle that is due to an electric field ____________ – the space around a charged object in which another charged object experiences an electric force

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CHARGE IT! Friction ________- occurs when electrons are “wiped” from one object to another Conduction __________ – electrons move from one object to another by direct contact.

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CHARGE IT! _________ – charges in an uncharged metal object are rearranged without direct contact with a charged object

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CONSERVATION OF CHARGE When you charge something by any method, ____________________________________. The numbers of ________ and _______ stay the same. Detecting Charge You can use a device called an _____________ to see if something is charged

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MOVING CHARGES __________- a material in which charges can move easily Examples: __________- a material in which charges cannot move freely Examples:

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STATIC ELECTRICITY _________________ electric charge at rest; produced from friction or induction _________________ – the release of electricity stored in a source

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1.2 ELECTRIC CURRENT & ENERGY _______________ – rate at which charges pass a given point When you flip a switch, an _____________ is set up in the wire at the speed of light. The electric field causes the _________ in the wire to move. This electric field is created so quickly that all electrons start moving through the wire _________. Think of the electric field as a command to the electrons to charge ahead.

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TYPES ELECTRIC CURRENT Direct Current (DC) ___________________ – charges always flow in one direction. Ex: Alternating Current (Ac) ___________________ – charges shift from flowing in one direction to flowing in the reverse direction EX:

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VOLTAGE AND ENERGY _______ – the potential difference between points SI unit : You can think of voltage as the amount of energy released as a charge moves between two points in the path of a current. As long as there is a voltage between _________, charges will flow in the wire. The ____ of the current depends on the _______

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Varying Nature of Voltage Different devices need different levels of voltage. 1.5 V 9 V 12 V

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Resistance ___________ – opposition to the flow of electric charge SI unit: Good conductors, such as copper, have _____________ Poor conductors, such as iron, have ______________ Resistance depends on thickness, length, & temperature Thick, _____ wires have ____ resistance than ____, thin wires. The resistance of metals _________ as temperature _________

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Resistance

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Generating Electrical Energy Remember energy is not created or destroyed – it only changes forms Parts of a Cell A cell contains a mixture of chemicals called an __________. Every cell also has a pair of __________made from conducting materials

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Types of Cells There are 2 types of cells: ___ – have an electrolyte Example: batteries – sulfuric acid is the electrolyte ___ – have a dry electrolyte Example: small radios or flashlights

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Generating Electrical Energy Cells change chemical or radiant energy into electrical energy. Batteries are made of one or more cells. ____________ can take thermal energy and transfer it to electrical energy. _________ convert light energy into electrical energy.

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1.3 ELECTRICAL CALCULATIONS How fast is a nanosecond? A nanosecond (ns) is one-billionth of a second. Electrical signals travel at 30 cm/ns. Calculate how far electrical signals travel in 1 second.

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CONNECTING CURRENT, VOLTAGE, AND RESISTANCE Georg Ohm Ohm (1789 –1854) studied the resistance of materials. He measured the current that resulted from different voltages applied to a piece of metal wire. Ohm’s Law – the ratio or voltage (V) to current (I) is the resistance (R) of a material V = I x R UnitSI Unit Voltage (V)V - volt Current (I)A- Amps Resistance (R) Ohm - Ω Electric Power

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OHM’S LAW CALCULATIONS Ex: 1 What is the voltage if the current is 2 A and the resistance is 12 Ω ? Ex: 2 Find the voltage if the current is 0.2 A and the resistance is 2 Ω

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OHM’S LAW CALCULATIONS Ex 3: The resistance of an object is 4 Ω. If the current in the object is 9 A, what is the voltage used? Ex 4: An object has a resistance of 20 Ω. Calculate the voltage needed to produce a current of 0.5 A.

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ELECTRIC POWER Electrical Power (P) – the rate at which electrical energy is converted into other forms of energy Si Unit: Watts (W) Power = voltage x current P = V x I UnitSI Unit Voltage (V)V - volt Current (I)A- Amps Power (P)W - Watts

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ELECTRICAL POWER CALCULATIONS Ex 1: A toaster draws approximately 10 A of current. A home receives 120 V at each electrical outlet. What is the power of the toaster? Ex 2: A car uses a 12 V battery. One headlight draws 3.0 A. What is the power of the headlight?

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ELECTRICAL POWER CALCULATIONS EX 3: A light bulb draws a 0.5 A current at a voltage of 120 V. What is the power rating of the light bulb?

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ELECTRICAL ENERGY Measuring Household Energy Use Different amounts of electrical energy are used each day in a home. Electric companies usually calculate electrical energy by multiplying the power in kilowatts by the time in hours.

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1.4 ELECTRIC CIRCUIT Just like a roller coaster, an electric circuit always forms a loop— it _____ and ____ at the ____ place Parts of an Electric Circuit (light bulb, appliance)

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SWITCHES Sometimes, a circuit also contains a _____ _____ – opens or closes a circuit _____ – electrons can ____ _____ – electrons _____________

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TYPES OF CIRCUITS ______________– a circuit in which the parts are joined one after another such that the current in each part is the same. _________for charges to follow – charges must flow through each part of the circuit The voltage across each load is _________ Series circuits are useful in wiring burglar alarms. If any part of the circuit fails, there will be __________in the system and the alarm will sound.

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TYPES OF CIRCUITS _______________- a circuit in which the parts are joined in branches so that the voltage (potential difference) across each part is the same Loads do ___have the _________________ Charges have more than ___ path to follow Parallel Circuits are used in almost all appliances and decorative string lights

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HOUSEHOLD CIRCUIT SAFETY Circuits can ____ if they are __________ or a wire breaks or has water damage. To prevent fire: A thin strip of metal in circuit that the charges flow through. If the current is too high, the metal will melt and the circuit is broken A switch that automatically opens if the current is too high. A metal strip heats up, bends, and opens the switch stopping the flow of current

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