Transcript Circuits
Circuits •A circuit always needs a power source, such as a battery, with wires connected to both the positive (+) and negative (-) ends. •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. 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 • Adding more batteries to a simple circuit will make a bulb brighter. Changing circuits Adding more bulbs to a simple circuit will make the bulbs dimmer. 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! 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! http://www.bbc.co.uk/schools/ks2bit esize/science/tests/changing_circui ts.shtml • http://www.bbc.co.uk/schools/ks2bitesize/s cience/tests/conductors.shtml http://www.bbc.co.uk/schools/ks2bitesize/science/tests/magnets_springs.shtml Magnets • When two magnets are close, they create pushing or pulling forces on one another. • These forces are strongest at the ends of the magnets. The two ends of a magnet are known as the north pole and the south pole. • If you try to put two magnets together with the same poles pointing towards one another, the magnets will repel (push away from) each other. • If you put two magnets together with different poles pointing towards one another, the magnets will attract (pull towards) each other. Some magnets are stronger than others. Strong magnets will create bigger pushing or pulling forces than weak magnets. • • • • Magnetic materials Magnets can attract other magnets but they can also attract magnetic materials. Magnetic materials are always metals but only a few metals are magnetic. Iron IS magnetic, so any metal with iron in it will be attracted to a magnet. Steel contains iron, so a steel paperclip, for example, will be attracted to a magnet. Most other metals, for example aluminum, copper and gold, are NOT magnetic. An aluminum drink can, for example, will not be attracted to a magnet. • Objects usually have equal numbers of positive and negative charges, but it isn't too hard to temporarily create an imbalance. Have you ever received a shock after walking across a carpet? As your feet shuffle across the carpet, they pick up extra electrons. Those electrons can't wait for you to touch something metal. As soon as your hand is close, they jump off with a shock and a spark of static electricity. • Atoms, the basic building blocks of matter, are made of three basic components: protons, neutrons and electrons. The protons and neutrons cluster together to form the nucleus, which is the central part of the atom, and the electrons orbit about the nucleus. Protons and electrons each carry a charge. Protons carry a positive charge while electrons carry a negative charge. Neutrons are neutral - they carry no charge at all. • A continuous flow of electrons creates an electric current. Materials that allow electricity to easily flow are called conductors. Electrical wires are made of metal because metal is one of the best conductors. One type of metal, copper, is most often used for electrical wires. Materials that do not allow electricity to pass easily through them are called insulators. Rubber, glass, plastic, cloth, and most non-metallic materials are poor conductors of electricity. This is why electrical wires are covered in rubber, plastic, or cloth. Electricians even wear rubber gloves when they are working with electrical wires. This does not mean that electricity cannot pass through insulators or any other material. If you give any object enough voltage (the force or push behind the flow of electricity), then that object will conduct electricity. Resistance slows down the flow of electrons is as it travels along the passageway of the wire. For example, longer electrical wires pose a greater amount of resistance to electricity than shorter wires. This is because the electricity has farther to travel.