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Magnetism Just the basics Magnetic Poles • Magnetic poles are LIKE ________________ _________________ • Like poles ________________ and opposite poles ________________. • They are caused by the movement of ________________ in the atoms of elements • The two poles are called ________________ and ________________ • All magnets are ________________ • This means that ________________ magnet, ____________________________________, has ________________ a north pole and a south pole Magnetic monopoles do not exist! • If I have a magnet, it has a north and south pole • If I cut the magnet in half… Each half will STILL have ________________________________________________ Magnetic Fields • Magnetic fields are VERY similar to ________________________________and we draw them the same way. • Magnetic field lines are drawn to point away from north and toward south • The symbol for magnetic field strength is ________________ • The unit magnetic field strength is measured in is ________________ Electricity and Magnetism • Hans Christian Oersted discovered that ANY time there is an ________________ ________________ (a moving electron) there is a ________________ ________________produced. • That magnetic field is ________________ to the current. First Right Hand Rule • This rule helps us find the direction of the magnetic field around a wire with current flowing through it. • Use your right hand – Point your thumb in the direction of the ________________ ________________. – The magnetic field wraps around the wire in the direction your fingers curl. • Example Second Right Hand Rule • This rule is used to find the ________________ of an electromagnet – Using your Right Hand – Curl your fingers in the direction of the ________________ ________________and your thumb will be pointing in the direction of the ________________ _______________ Michael Faraday • Faraday discovered that when a current carrying wire is placed inside a magnetic field, the magnetic field will cause a ________________ to be applied to the wire. • The direction of this force can be found by yet another right hand rule Third Right Hand Rule • Used to find the direction of the ________________ acting on a current carrying wire in a magnetic field • Using the right hand – Point your thumb in the direction of the ________________ _______________ and your index finger in the direction of magnetic field. The force will be in a direction ________________ of your palm. Pictures of the right hand rules (in order) Electromagnetic Induction • Oersted discovered that an electric current causes a magnetic field. • Faraday discovered that if a wire is moved while in a magnetic field, then the magnetic field will cause (induce) an electric current. • This is how electric ________________ work – Most of the time however, we move the ________________ instead of the ________________ – It is also how ________________ ________________ ________________work Alternating Current • When a magnet is spun inside of a coil of wire in a generator, the ________________ of the north and south pole is ________________ changing. • This causes the direction of the current induced in the wire to change – This is called ________________ ________________ ________________ Electric Transformers • Transformers are devices that use electromagnetic induction to ________________ or ________________ the ________________ in a circuit. • How much the voltage is stepped up or down depends on the ________________ ________________ ________________on each side Calculating Voltage of a Transformer • The voltage in the primary and secondary coils have the same ratio as the number of turns in the coils • Use the following equation Example 1 • What is the resulting voltage in the secondary coil of 40 turns if the primary coil has 20 turns and a voltage of 60V? Example 2 • I have a circuit with a voltage of 120 V. If I wrap this wire around an iron core 3000 times, how many times will I need to wrap a second wire to produce a voltage of only 6 V?