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Download Natural Science, Unit 8: Electricity and Magnetism
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Natural Science, Unit 8: Electricity and Magnetism This slideshow will tell you everything you need to know from Unit 8 of Natural Science… Pay attention! Insulators • Insulators are materials that do not pass energy through them easily. • Examples include: glass, plastic, porcelain, rubber and wood. • We use insulators to protect ourselves from electricity. • Insulators can also be called non-conductors. Conductors • Conductors are dense materials that pass energy between particles easily. • Examples include: copper, water and silver. Benjamin Franklin • He created the lightning rod, which is important for modern society as it helps to protect us from being struck (hit) by lightning! • He used a kite and a Leyden jar (which stored electrical energy like a battery) to learn about electricity. HANS CHRISTIAN ØRSTED (1777-1851) • Hans Christian Orsted discovered the relationship between electricity and magnetism. • The unit for measuring magnetism- Oerstedis named after him. • His discoveries led to the development of electromagnets. Electricity Electricity begins in atoms. • Atoms are made of protons and neutrons inside a nucleus. • Electrons move around outside the nucleus. • Protons have a positive electrical charge. • Neutrons have no electrical charge. • Electrons have a negative electrical charge. • Electrons can sometimes move easily from one object to another, which results in objects becoming electrically charged. Electricity is the movement of electrons. Electrical charges • Electrical charges repel or attract each other, the same as magnets. • Negative charges are attracted to positive ones. • Negative repels negative and positive repels positive. Static electricity • Static means ‘still’ or ‘not moving’. • Static electricity is a form of electricity that doesn’t flow. • If static electricity forms a negative charge, it will be stored in particles until a positively charged object is nearby. Then, it will ‘jump’ from negative to positive. • The electric shock feeling that you get from a supermarket trolley or a slide is made possible by static electricity. Current Electricity • When electrons move from one object to another, this creates electrical current. • We can trap this in a circuit using conductors like copper or silver wires . Electrical Circuits • Closed electrical circuits pass the flow of electrons around in a circle. • An electrical circuit has the following parts: – A power source provides energy – Wires conduct electricity – A switch opens and closes the circuit – A resistor changes the electricity into different types of energy Magnetism • Can be natural (like certain minerals) or man-made, like electro-magnets. • Minerals such as magnetite, iron, nickel and cobalt are magnetic. Types of magnets • Permanent magnets never lose their magnetism • Induced or temporary magnets lose their magnetism over time • Magnets have poles (ends), the same as planet Earth- North and South. • If you put two North poles together, they will push each other apart (repel). • If you put two South poles together, they will repel. • If you put North and South together, they will move towards each other. This is called magnetic attraction. Magnetic Field • The liquid iron core of Earth makes it act like a huge magnet. • It creates a magnetic field, like all magnets, that protects us from cosmic rays and protects our atmosphere. • Some parts of cosmic rays can enter the atmosphere at the magnetic North and South poles. We can see them as lights- the Aurora Borealis (North) and the Aurora Australis (South). • • • The more magnetic something is, the bigger its magnetic field will be. The area around a magnet that attracts magnetic objects is called a magnetic field. We can see a magnetic field by putting a magnet in an area of magnetic iron filings. What things are magnetic? Magnetic materials are always metallic, but not all metals are magnetic. • Iron and steel (but not stainless steel) are magnetic. • We can make magnets from other, non-magnetic metals that are good conductors. • Electromagnets are magnets created by passing electricity through certain types of metal objects to create a magnetic field. Electromagnets What do we use electromagnets for? Electromagnets are used in security, trains, speakers, disks, microphones, hairdryers, TVs, keycards, bank cards and MRI scanners. These are just a few examples!