How is lightning similar to getting an electric shock when you reach for a metal door knob?
Electricity Electric charges are from protons, which are positive (+) and electrons, which are negative (-). Static electricity accumulation of excess electric charges on an object. Atoms become charged by gaining or losing electrons.
Law of Conservation of Charge - Electric charges can be transferred from object to object, but it cannot be created nor destroyed. Positive and negative charges exert forces on each other (+) (-) (+) (+) Opposites attract Likes repel
Conductors vs. Insulators Conductors materials in which electrons move easily. Ex. metals Insulators materials in which electrons are not able to move easily. Ex. wood, plastic, rubber
Charging Objects Charging by contact process of transferring charge by touching or rubbing. Charging by induction rearrangement of electrons on a neutral object caused by nearby charged objects.
What property of electric current allowed Edison s first lightbulb to light?
Electric Current Electric current The net movement of electric charges in a single direction through a wire or conductor. Voltage difference The force that causes electric charges to flow; charges flow from high voltage to low voltage.
Circuit A closed path that electric current follows Circuits include a power source (battery), wires, and some resistor (light bulb) and a voltage difference allows current to flow.
Batteries Dry Cell Chemical reactions occur in a moist paste causing the transfer of electrons Ex. AA or D battery Wet Cell Contains two connected plates made of different metals in conducting solution. Ex. Car battery
Resistance The tendency for a material to oppose the flow of electrons, changing electrical energy into thermal and/or light energy. Ex. Light bulb, dial, switch, heating coil * Making wires thinner, longer, or hotter increases resistance.
All materials have some electrical resistance measured in ohms (Ω). Ohm s Law current in a circuit equals voltage difference divided by the resistance. Current (I) = voltage difference (V) resistance (R ) Current measured in amps (A), voltage difference measured in volts (V), resistance measured in ohms (Ω)
Why does your home have a circuit breaker or fuse box?
Circuit Symbols Wire (conductor) Light bulb Closed switch Open switch Battery
Circuit Types Series Circuit Current has only one loop to flow through. Ex. Flashlight, holiday lights Parallel Circuit Contains two or more branches for current to flow through. Ex. Homes, autos.
Circuit Types Series Circuit Parallel Circuit
Complex Circuit A circuit composed of both series and parallel circuits.
Electrical energy enters your home at the circuit breaker or fuse box and branches out to appliances, wall sockets, and lights. Circuit breaker small piece of metal that bends when it gets hot, opening the circuit and stopping current flow Electric fuse small piece of metal that melts if current becomes too high, opening the circuit
Question Why are magnets so important?
Magnetism magnetism - refers to the properties and interactions of magnets in which there is a force of attraction or repulsion between like or unlike poles. Strength of force between two magnets depends on the distance between them.
magnetic field - exerts a force on other magnets and objects made of magnetic materials. (strongest is closest to the magnet)
All magnets have a north pole and a south pole. Magnetic materials Only a few metals, such as iron, cobalt, and nickel are attracted to magnets or can be made into permanent magnets.
magnetic domains - group of atoms with aligned magnetic poles (too small to be seen with the eye) permanent magnets - are made by placing a magnetic material in a strong magnetic field, forcing magnetic domains to line up.
question How does a stereo speaker use an electromagnet to produce sound?
Magnetism and Electricity When electric current flows through a wire, a magnetic field forms around the wire. Strength of magnetic field depends on the amount of current flowing in the wire.
electromagnet - a temporary magnet made by wrapping a wire coil carrying a current around an iron core. Increased strength of the magnetic field occurs by adding more turns to the wire coil (solenoid) or increasing the current passing through the wire.
electric motor - a device that changes electrical energy into mechanical energy. In a simple electric motor, an electromagnet rotates between the poles of a permanent magnet.
Direct and Alternating Current direct current (DC) - current that flows in only one direction through a wire Ex. a battery alternating current (AC) - reverses the direction of the current flow in regular patterns. Ex. plugging a toaster into a wall outlet