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Name________________________________ Block ________________________________________ Now, we will learn: (3 main ideas on top of the page) _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ _________________________________________________________________________________ An electric current produces a magnetic field Like many discoveries, the discovery that electric ___________________ is related to _________________ was unexpected. In the 1800s, a Danish physicist named Hans Christian Oersted (UR-stehd) was teaching a ___________ class. Oersted used a _______________ and _______________ to demonstrate some properties of ____________________. He noticed that as an _____________________________ passed through the ______________, the needle of a nearby _________________ moved. When he turned the __________________ off, the needle __________________ to its original direction. After more experiments, Oersted confirmed that there is a _______________________ between magnetism and electricity. He discovered that an ___________________________________ produces a ____________________________. Electromagnetism The ___________________ between electric ______________ and ________________ plays an important role in many ______________ technologies. ______________________ is magnetism that __________________ __________________________ such as from an an electric current. ___________________ When a moves, it _______________ a magnetic field. Because an __________________________ generally 1 consists of ________________ electrons, a ________________ in a wire _______________ a magnetic field. In fact, the _____________ acts as a ______________. Increasing the ________________ of current in the wire ________________ the strength of the magnetic field. Copy the diagram showing how a magnetic field surrounds a current carrying wire The ________________________ of a wire actually forms the ___________ of a _________ around the wire. The ____________________ of the ________________ determines the __________________ of the magnetic field. If the __________________ of the electric current is ___________________, the magnetic field still exists in circles around the wire, but is __________________. If the wire is ________________ into a ______________, the magnetism becomes _________________________ inside the loop. The field is much ________________ in the _____________ of the _____________ than it is around a straight wire. If you _____________ the wire into a _______________, the magnetic force becomes ___________________ with each _____________________________ of wire as the magnetic field becomes more __________________________. Copy the diagram showing the magnetic field with a coil Why is the magnetic field stronger when we wrap the wire into a coil, where would you expect to have the strongest magnetic field? 2 How is a coil of wire that carries a current similar to a bar magnet? A coil of wire with charge flowing through it has a magnetic field that is similar to the magnetic field of a bar magnet. Inside the coil, the field flows in one direction, forming a north pole at one end. The flow outside the coil returns to the south pole. The direction of the electric current in the wire determines which end of the coil becomes the north pole. Making an Electromagnet Recall that a piece of ____________ in a strong magnetic field becomes a ______________ itself. An _______________________is a magnet made by placing a _____________________ or _________________ inside a ______________ of wire. As long as the ____________ carries a __________________, the metal acts as a magnet and __________________ the magnetic field of the coil. But when the current is turned _________, the magnetic ______________ in the metal ____________________________ again and the magnetic field __________________. How can Jimmy increase or decrease the strength of the electromagnet? Jimmy 3 Uses of Electromagnets Use the following mind map to identify 4 main ideas for the uses of electromagnets: Uses for electromagnets Motors use electromagnets Because magnetism is a ______________, magnets can be used to ______________________. Electric motors _______________ the ________________ of an electric current into ________________ by taking advantage of the _______________________ between ____________ and ___________________. There are hundreds of ________________ that contain ________________ motors. Examples include power ______________, electrical _______________ appliances, and the small ____________ in a computer. Almost anything with _______________ parts that uses _______________ has an electric ______________. Motors Label the parts of the DC (Direct Current) motor 4 Label the indicated parts: What is a commutator? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Describe how a basic electric motor works: Why does an electric motor have to use an electromagnet rather than a permanent magnet to rotate the shaft of an electric motor? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 5 Uses of Motors There are many uses for electric motors. Read the section on "Uses of Motors" and try to pick out 5 different uses for electric motors: 1. _________________________________________ 2. _________________________________________ 3. _________________________________________ 4. _________________________________________ 5. _________________________________________ Now try to think of 3 more on your own: 1. _________________________________________ 2. _________________________________________ 3. _________________________________________ Energy (this part is not in the book) – you must use your head. Energy cannot be created nor can it be destroyed – it can only change forms Electrical Energy – energy in the form of electricity that has the potential to do work Kinetic Energy – the energy of motion Question: How does a motor turn electrical energy into kinetic energy? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ 6