Electricity and Magnetism Circuits Electromahnets

Electricity and MagnetismCircuitsElectromagnetsChapter 17 and 18How can you produce electricity?...right now!

The Law of Electric ChargeLike charges repel push away

Opposites attract

Electric FieldA region around a charged object in which an electric force is exerted on another charged object.Charge It How do we create charge?Friction electrons are wiped from one object to anotherConduction electrons move through direct contact (a shock!)Induction when charges are rearranged without direct contact

What is an electric circuit?A complete loop (begins and ends at the same place) through which electric charges flow.

VoltageThe unit of measure for potential difference is the Volt (V)Think 9 volt batteryThe device that provides the potential difference is considered the voltage source;

CurrentThe current is the rate at which a charge passes a given pointThe unit for current is the ampere or Amp (symbol - A)An amp is the amount of current that flows past a point in one second

How does the flow begin?Electrons in a circuit have potential energyThe potential energy of each charge is called electrical potentialIn a battery, the electrical potential of one terminal is higher than the other terminalThe difference in this potential energy is called potential differenceThis potential difference causes the loose electrons to be pulled away from their atoms and flow through the materialThe Essential Parts of a CircuitAn energy source battery etc.Wires to carry the electric chargeLoad light bulb, radio etc.

SwitchesSome circuits in include a switch to open and close the circuit (turn it on and off)Open off (the loop is broken)Closed on (the loop is closed or complete)

Types of CircuitsThe parts of a circuit can be connected in different ways. The two main types are:SeriesParallel

Series CircuitsAll parts are connected in a single loop

All loads in a series circuit share the same currentSeries Circuit Will all bulbs burn with the same brightness?Yes, all receiving the same electric current.What will happen if I add a bulb?They will all dim b/c they will receive less electric current.What happens if one bulb burns out?They will all go out, the loop is no longer complete.

Parallel CircuitA circuit in which loads are connected side by sideCurrent in a parallel circuit has more than one pathEach load receives the full amount of energy the energy source can provide (voltage) and they will use as much current as they needEx. 45 vs. 60 Watt light bulbParallel CircuitsWill all bulbs burn with the same brightness?No, it depends on their wattage.What will happen if I add a bulb?They will continue to burn with the same brightness.What happens if one bulb burns out?The remaining bulbs will stay lit.

Questions to Consider:Which circuit would be more useful in lighting a home or building?Parallel, you want to be able to have the lights on in one room and off in another.Which circuit is used in Christmas tree lights?It depends, they used to be made in series, if one burned out all went out. Nowadays many are made in parallel so the remaining bulbs will continue to burn.Why are series circuits useful?Burglar alarmsWhat drawbacks are there in using parallel circuits?How does a compass work?It is a magnet that works, moving from its north/south orientation only when it is no longer aligned with the earths poles

A man, Hans Oersted, found that when a compass is held near a wire that is passing electric current the compass would move even if it was still aligned with the poles. What is a solenoid?Electricity and magnetism are closely related. This was first seen when a solenoid was developed.

A solenoid is simply a coil of wire that when current is flowing through it will generate a magnetic field.

Electromagnet:A stronger version of the solenoid!It creates a temporary magnet when a current-carrying wire coil surrounds a magnetic metal core.Useful because they can be turned offAdding and removing coils can increase or decrease strength