CHAPTER 1

ELECTRICITY

ELECTRIC CHARGE

• Charges Exert Force• Atoms are composed of particles with ______. The

law of electric charges states that like charges _____and opposite charges _______

THE FORCE BETWEEN PROTONS AND ELECTRONS

• Protons and electrons have ________ charges, they are ________ to each other

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

CHARGE IT!

Friction

• ________- occurs when electrons are “wiped”

from one object to another

Conduction

• __________ – electrons move from one object to another by direct contact.

CHARGE IT!

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

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

MOVING CHARGES

• __________- a material in which charges can move easily• Examples:

• __________- a material in which charges cannot move freely

• Examples:

STATIC ELECTRICITY

• _________________ electric charge at rest; produced from friction or induction

• _________________ – the release of electricity stored in a source

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.

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:

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 _______

Varying Nature of Voltage

• Different devices need different levels of voltage.

1.5 V 9 V 12 V

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 _________

Resistance

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

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

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.

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.

•

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 Unit SI Unit

Voltage (V) V - volt

Current (I) A- Amps

Resistance (R)

Ohm - Ω

Electric Power

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

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.

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

Unit SI Unit

Voltage (V) V - volt

Current (I) A- Amps

Power (P) W - Watts

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?

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?

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.

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)

SWITCHES

• Sometimes, a circuit also contains a _____

• _____ – opens or closes a circuit• _____ – electrons can ____• _____ – electrons _____________

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 thecircuit fails, there will be __________in the system and the alarm will sound.

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

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