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Lesson 2 Magnetism Guided Notes Magnetic Force • Depending on which ends of the magnets are close together, the magnets either ________ or _________ each other. • The strength of the force between two magnets _______________ as magnets move closer together and _______________ as the magnets move farther apart. Magnetic Field • A magnet is surrounded by a magnetic ____________. A magnetic field exerts a force on other magnets and objects made of magnetic materials. • The magnetic field is _____________ close to the magnet and ______________ far away. How Magnets Interact • Two magnets can either _________ or ___________ each other. • Two north poles or two south poles of two magnets __________ each other. However, north poles and south poles always _____________ each other. • When two magnets are brought close to each other, their magnetic fields combine to produce a new magnetic _______________. Magnetic Field Direction • When a ______________ is brought near a bar magnet, the compass needle rotates. • The force exerted on the compass needle by the magnetic field causes the needle to ___________. • The compass needle rotates until it lines up with the _________________ field lines. • The _____________ pole of a compass points in the direction of the magnetic field. • This direction is always away from a ________ magnetic pole and toward a ________ magnetic pole. Earth’s Magnetic Field • A compass can help determine direction because the north pole of the compass needle points ________. • This is because Earth acts like a giant bar __________ and is surrounded by a magnetic field that extends into space. • Just as with a bar magnet, the compass needle aligns with Earth’s _______________ field lines. Earth’s Magnetic Poles • Currently, Earth’s south _____________ pole is located in northern Canada about 1,500 km from the _______________ North Pole. • Earth’s magnetic poles move ___________ with time. Magnetic Materials • You might have noticed that a magnet will not attract all ____________ objects. • Only a few metals, such as ________, _________, or ___________, are attracted to magnets or can be made into permanent magnets. • What makes these elements magnetic? Remember that every atom contains ____________. • In the atoms of most elements, the magnetic properties of the electrons ___________ out. • But in the atoms of iron, cobalt, and nickel, these magnetic properties _________ cancel out. • Even though these atoms have their own magnetic fields, objects made from these metals _________ always magnets. Nonmagnetized Materials • __________________________ materials can be magnetized because they contain magnetic domains • These magnetic domains are not normally _______________, but they have the potential to be aligned when in the presence of ______________________ fields. Ex…iron nail. • A – outside of the presence of a magnetic field, no magnetism • B – within a ______________________ field, the material becomes magnetized. • When ____________________ from the magnetic field, the material is no longer a magnet Electric Current and Magnetism • In 1820, Han Christian Oersted, a Danish physics teacher, found that electricity and magnetism are _____________. • Oersted hypothesized that the electric current must produce a _____________________ around the wire, and the direction of the field changes with the direction of the ______________. Moving Charges and Magnetic Fields • It is now known that _____________ charges, like those in an electric current, produce magnetic fields. • Around a current-carrying wire the magnetic field lines form ______________. • The direction of the magnetic field around the wire ______________ when the direction of the current in the wire reverses. • As the current in the wire ____________ the strength of the magnetic field _____________. Electromagnets • An __________________ is a temporary magnet made by wrapping a wire coil carrying a current around an iron core. • When a current flows through a __________ loop, the magnetic field inside the loop is stronger than the field around a straight wire. • A single wire wrapped into a cylindrical wire coil is called a _______________. • The magnetic field inside a solenoid is _____________ than the field in a single loop. • If the solenoid is wrapped around an __________ core, an electromagnet is formed. • The solenoid’s magnetic field _______________ the iron core. As a result, the field inside the solenoid with the iron core can be more than 1,000 times greater than the field inside the solenoid without the iron core. Properties of Electromagnets • Electromagnets are _______________ magnets because the magnetic field is present only when current is flowing in the solenoid. • The strength of the magnetic field can be ________________ by adding more turns of wire to the solenoid or by increasing the current passing through the wire. • One end of the ______________________ is a north pole and the other end is a south pole. • If placed in a magnetic field, an electromagnet will __________ itself along the magnetic field lines, just as a compass needle will. • An electromagnet also will _________ magnetic materials and be attracted or repelled by other magnets. Making an Electromagnet Rotate • The forces exerted on an electromagnet by another magnet can be used to make the electromagnet _______________. • One way to change the forces that make the electromagnet rotate is to change the _____________ in the electromagnet. • Increasing the current _________________ the strength of the forces between the two magnets.