SAFETY CHECK Do not play with electricity. Do not place objects on top of electrical cords or wires because the wires may become damaged. When using electrical devices, follow all instructions. When you remove a plug from a wall outlet, use the plug; do not pull on the cord.

OPPOSITES ATTRACT Now, positive and negative charges behave in interesting ways. Two things with opposite, or different charges (a positive and a negative) will attract, or pull towards each other.

REPEL Things with the same charge (two positives or two negatives) will repel, or push away from each other. 


ELECTRICAL CHARGE If two things have the same charge, they repel, or push away from each other. If two things have different charges, they attract, or pull towards each other. LIKE CHARGES REPEL UNLIKE CHARGES ATTRACT

STATIC ELECTRICITY We notice static electricity in the winter when the air is very dry. During the summer, the air is more humid. The water in the air helps electrons move off you more quickly, so you can not build up as big a static charge.

STATIC ELECTRICITY

STATIC ELECTRICITY In a thunder and lightning storm. Clouds become negatively charged as ice crystals inside the clouds rub up against each other. Meanwhile, on the ground, the positive charge increases. The clouds get so highly charged that the electrons jump from the ground to the cloud, or from one cloud to another cloud. This causes a huge spark of static electricity in the sky (lightning).

STATIC ELECTRICITY

STATIC ELECTRICITY When you take off your wool hat, it rubs against your hair. Electrons move from your hair to the hat. A static charge builds up and now each of the hairs has the same positive charge. Remember, things with the same charge repel each other. So the hairs try to get as far from each other as possible. The farthest they can get is by standing up and away from the others. And that is how static electricity causes a bad hair day!

STATIC ELECTRICITY So, why does your hair stand up after you take your hat off? When you pull your hat off, it rubs against your hair. Electrons move from your hair to the hat. Now each of the hairs has the same positive charge. Things with the same charge repel each other. So the hairs try to move away from each other. The farthest they can get is to stand up and away from all the other hairs.

STATIC ELECTRICITY As you walk across a carpet, electrons move from the rug to you. Now you have extra electrons and a negative static charge. Touch a door knob and ZAP! The door knob is a conductor. The electrons jump from you to the knob, and you feel the static shock.

STATIC ELECTRICITY

ELECTRICAL CURRENT A continuous flow of negative charges (electrons) electric charges flow steadily, like currents of water in a stream.

Electron flow (negative) ELECTRIC CURRENT Electron flow (negative)

ELECTRIC CIRCUIT A path along which negative charges can flow. A simple electric circuit starts with a source of electric charges like a battery. A wire connects the source to a light bulb or another device. A second wire connects the bulb back to the source of negative charges.

CIRCUITS When you flip a light switch on and off, you are closing and opening a circuit. A circuit is the path that electricity follows. For electrons to travel (creating an electric current), the circuit must be closed. When you flip the light switch off, you are opening the circuit and the lights turn off. When you flip the switch on, the circuit it closed and the lights come on.

CIRCUITS A circuit can also contain other electrical components, such as bulbs, buzzers or motors, which allow electricity to pass through. Electricity will only travel around a circuit that is complete, i.e. has no gaps.

CIRCUITS

OPENED CIRCUIT Incomplete Circuit The circuit is opened and electricity can not flow through the path.

OPENED CIRCUIT

CLOSED CIRCUIT Complete Circuit Electricity can flow through the path.

CLOSED CIRCUIT

ELECTRICAL CONDUCTORS

CHANGING CIRCUITS 1. Circuits A circuit always needs a power source, such as a battery, with wires connected to both the positive (+) and negative (-) ends.

CHANGING CIRCUITS 2. Switches When a switch is open (off), there is a gap in the circuit. Electricity cannot travel around the circuit. When a switch is closed (on), it makes the circuit complete. Electricity can travel around the circuit.

CHANGING CIRCUITS 3. Adding more batteries to a simple circuit will make a bulb brighter.

CHANGING CIRCUITS 4. Adding more bulbs to a simple circuit will make the bulbs dimmer.

CHANGING CIRCUITS 5. Lengthening the wires in a simple circuit will make the bulb dimmer.

ELECTRIC CIRCUIT A path along which negative charges can flow. A simple electric circuit starts with a source of electric charges like a battery. A wire connects the source to a light bulb or another device. A second wire connects the bulb back to the source of negative charges.

CIRCUITS AND CONDUCTORS 1. Electrical conductors Some materials let electricity pass through them easily. These materials are known as electrical conductors. Many metals, such as aluminum, copper, iron and steel, are good electrical conductors. That is why the parts of electrical objects that need to let electricity pass through are always made of metal.

CONDUCTORS Metal Copper Iron Steel

ELECTRICAL INSULATORS Some materials do not allow electricity to pass through them. These materials are known as electrical insulators. Plastic, wood, glass and rubber are good electrical insulators. That is why these materials are often used to cover materials that carry electricity.

ELECTRICAL INSULATORS wood rubber plastic glass

PARALLEL CIRCUIT It has more than one path for an electric current to follow as shown in this picture.

PARALLEL CIRCUIT In path 1, negative charges can flow from the battery through bulb A and back to the battery. In path 2, negative charges can flow from the battery through bulb B and back to the battery. When both bulbs are in place, current will follow both paths, and both bulbs will be lighted. If either bulb is removed, current will still follow the path through the other bulb. The bulb in this part of the circuit will remain lighted.

Series Circuit All of the parts are connected one after the other in a single loop, or path.

SERIES CIRCUIT If either bulb is removed from the circuit, the circuit is broken and the current stops. If one of the light bulbs in this string of Christmas lights does not work, then all of the lights do not turn on.

ELECTRIC CURRENT Electron flow (negative) A continuous flow of negative charges (electrons) electric charges flow steadily.

Path Route or course

Circuit Complete path of electric current Parallel Circuits