ELECTRICITY NOTES

ELECTRICITY ELECTRICITY: form of energy that occurs when electrons move from place to place Electricity can form whenever (e - ) electrons are gained or lost

All substances are made up of ATOMS which contain electrically charged particles called PROTONS and ELECTRONS PROTONS have a positive (+) charge ELECTRONS have a negative (-) charge

How can neutral substances become electrically charged? – When a neutral object slides past another object and picks up extra e - –An object with more protons has a + charge –An object with more electrons has a - charge

STATIC ELECTRICITY STATIC ELECTRICITY is a buildup of electrons on an object

CONDUCTORS: allow electrons to pass through easily –Examples: METALS, WATER INSULATORS: do NOT allow electrons to pass through easily –Examples: NONMETALS

When 2 objects are rubbed together they become CHARGED Objects with like charges REPEL Objects with opposite charges ATTRACT

INDUCTION INDUCTION occurs when a neutral object becomes charged by holding a charged object close to it ( NOT touching)

How is Earth’s Surface Charged by Induction?

An ELECTROSCOPE is a devise that detects electric charge. A metal knob is connected to 2 metal leaves. When a charged object touches the knob, the leaves SEPARATE

GROUNDING GROUNDING : touching a charged object to the ground to remove extra charges

Moving charges produce CURRENT ELECTRICITY which flows along a path called a CIRCUIT. Current that only flows in one direction is called DIRECT CURRENT (battery powered). Current that reverse its direction constantly is called ALTERNATING CURRENT (AC) (power company)

ELECTRIC CURRENT (I) THE FLOW OF e - (how many are flowing through each second) Units: AMPERES (A) 1 AMPERE = 6.25 X10 18 e - EACH SECOND

ELECTRIC CELL An ELECTRIC CELL is a devise that converts chemical energy into electrical energy. 2 or more electric cells combined make up a BATTERY. An electric cell contains two different substances called ELECTRODES. The electrodes are places in a conducting mixture called an ELECTROLYTE. Chemical reactions take place between the ELECTRODES and the ELECTROLYTE.

Wet Cell: a battery with a liquid electrolyte…acid (car battery) Dry Cell: battery whose electrolyte is a paste instead of a liquid (AA, C, D batteries, etc) Anode: - end of battery where e - leave the battery Cathode: + end of battery where e - return to the battery

VOLTAGE (V) also called POTENTIAL DIFFERENCE. It is the difference between one end of the power source and the other end. –Units : VOLTS (V)

RESISTANCE (R) RESISTANCE is the opposition to electron flow. Conductors have LOW resistance. Insulators have HIGH resistance. –Units: Ohms Ω Resistance depends on TEMPERATURE, DIAMETER, LENGTH, METVAL vs. NONMETAL

Ohms Law V = IR voltage = current x resistance

The filament in a light bulb uses a current of 0.5 A when the voltage is 120V. What is its resistance?

Circuits A path for electrons to travel through is called an ELECTRIC CIRCUIT If an electron can flow in a complete path, the circuit is A CLOSED CIRCUIT If a connection is broken along the circuit, it becomes AN OPEN CIRCUIT Switch: A DEVICE THAT CAN OPEN A CIRCUIT

Simple Circuits Made up of 1. power source (battery, generator) 2. conductor (wire) 3. load (bulb, resistor, motor)

SAFETY DEVICES on CIRCUITS that PREVENT FIRES 1.CIRCUIT BREAKER: switch that opens when current is too high 2.FUSES: a switch that melts when current is to high

TYPES OF CIRCUITS A SERIES CIRCUIT only has 1 path for electrons A PARALLEL CIRCUIT has more than one path for electrons.

Short Circuits Short Circuit: when uninsulated wires touch and the e - take a shorter path; can overheat and cause a fire

Electric Power The amount of electrical energy used each second is called ELECTRIC POWER, RATE AT WHICH ENERGY IS CONVERTED Units: Watts (w) or Kilowatts (kW) Formula: P = VI Power = Volts x Current

How much electrical power is used by a TV that uses a current of 0.5A when connected to a voltage of 120V?

Electrical Energy Power E = Pt energy = power x time

A hairdryer with a power rating of 1500W is used for 120 seconds. How much electrical energy does it use?

Kilowatt-hour The unit for energy used by the power company