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Magnetic Fields Review
Transcript of Magnetic Fields Review
the fridge? Different Types of Magnets opposite points on the surface of a magnet where magnetic forces are strongest
any influence that causes an object to move
to push away by a physical force
to pull in by a physical force Poles: Repel: Attract: Key Definitions Now I can... Draw a picture of two magnets repelling and two magnets attracting Define the terms attract and repel Magnets attract or repel other magnets Force: Magnetic Flux A measure of the quantity of magnetism
Dependent on the strength of the magnetic field
Scalar quantity A product of the average magnetic field and the perpendicular area that it penetrates
The number of field lines that 'cut through an area'
Measured in webers, Wb Magnetic Flux Density, B The magnetic field is stronger if there are more field lines in a given area
The density of flux is larger
Measured in Tesla, T The three magnetic elements are:
Iron - Fe
Nickel - Ni
Cobalt - Co
Only materials made of these elements will experience a magnetic force Moving Charges Moving charges create a magnetic field
All wires have a magnetic field around them when a current is flowing
The direction of the magnetic field can be found using the right-hand grip rule Current-Carrying Conductors & Fleming's Left-Hand Rule When a wire carries a current it has a magnetic field around it
Placing a wire into a magnetic field results in the two magnetic fields interacting
The wire will either be attracted or repelled from the fixed magnet The force experienced is at a maximum
when the current flowing is perpendicular
to the field lines of the magnet The force experienced is at a minimum
when the current flowing is parallel
to the field lines of the magnet The size of the force on the wire can be increased by: Increasing the strength of the magnetic field it experiences
Increasing the size of the current flowing through it
Increasing the number of turns of wire experiencing the magnetic field Charges & Magnetic Fields All charges produce a magnetic field
If a charged particle is placed in a magnetic field then it will experience a force
Fleming's Left-Hand rule can be used to determine the direction of this force The maximum force is when the particle is traveling perpendicular to the flux The 2nd finger represents the velocity vector of positive charge movement
When there is a negative charge the direction is opposite to the velocity vector of that particle! The minimum force is when the particle is traveling parallel to the flux Now I can... Apply Fleming's Left-Hand rule to charges Define the terms flux and magnetic flux density Apply Fleming's Left-Hand rule to currents Electromagnetic Induction Moving a magnet into a coil induces a voltage across the ends of the wire - a current is induced in the wire Faraday's Law
The size of the induced voltage depends upon the 'rate of cutting of magnetic flux lines' Using a Stronger Magnet The magnetic field lines are closer together
More lines of flux are cut in a given time If the Coil Face has a Bigger Area The total flux intercepted by the coil would be larger Increasing the Number of Turns More turns mean that more lines of flux will be 'cut' Increase the Speed of the Magnet More lines of flux are 'cut' in a shorter space of time Induced emf & Fleming's Right Hand Rule The direction of the induced emf can be found using Fleming's Right-Hand Rule Lenz's Law This is called the Dynamo Effect Caused by movement between a conductor and a magnetic field The induced emf must cause a current to flow in such a direction as to oppose the change in flux linkage that produces it Flux Linkage The number of magnetic flux lines passing through a coil of wire
Dependent on the number of turns, N, on the coil and the quantity of the magnetic field
Measured in weber-turns Now I can... Define the term Flux Linkage
Describe and explain Faraday's Law & Lenz's Law
Explain the factors that affect the emf induced in coil
Apply Fleming's Right-Hand rule to determine the direction of an induced emf