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CHAPTER 19: MAGNETISM. Section 19.1-2: Magnets, Magnetic Fields, & Electricity. PROPERTIES OF MAGNETS. A magnet has 2 poles – north & south Like poles repel, opposites attract If you break a magnet, the 2 new pieces will have a north and south pole.
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CHAPTER 19:MAGNETISM Section 19.1-2: Magnets, Magnetic Fields, & Electricity
PROPERTIES OF MAGNETS • A magnet has 2 poles – north & south • Like poles repel, opposites attract • If you break a magnet, the 2 new pieces will have a north and south pole. • Some metals can become magnetized by being brought near a magnet. They are called temporary magnets.
MAGNETIC FIELDS AROUND MAGNETS • Just like electric and gravitational forces result from electric and gravitational fields, magnetic forces result from magnetic fields. • These fields move from north to south. • A compass always points from the North to the South.
MAGNETIC FIELDS AROUND MAGNETS • The number of magnetic field lines passing through a surface is called the magnetic flux. • The flux per unit area is proportional to the strength of the magnetic field . • The Earth has a magnetic field. • The magnetic north does not coincide with the geographic North Pole since the axis of the Earth’s magnetic field does not lie along its rotational axis. • The Earth’s magnetic field fluctuates and has changed its position over time.
Magnetism from Electricity • Hans Christian Oersted found that a compass needle was deflected when brought near a current-carrying wire. • We can find the direction of this current using the “right hand rule”.
RIGHT-HAND RULES • First Right-Hand Rule- finds the direction of the magnetic field in a current-carrying wire • Use your right hand! • Grasp wire with right hand. • Keep thumb pointed in direction of positive current flow. • Your fingers will circle the wire and point in the direction of the magnetic field (p. 685)
CHAPTER 19:MAGNETISM Section 19.3: Magnetic Force
MAGNETIC INDUCTION • The strength of a magnetic field is called magnetic induction. • It is symbolized by B • It is measured in Teslas (T). 1 T = 1N/A.m
MAGNETIC INDUCTION We can use two formulas to find magnetic force: F = BIL F = qvB Where B = strength of magnetic field I = current q = charge L = length of wire v = velocity of charge
ANOTHER RIGHT-HAND RULE • Second Right-Hand Rule - determines the direction of force in a magnetic field. • Use your right hand! • Point your fingers in the direction of the magnetic field. • Point your thumb in the direction of the positive current flow.
ANOTHER RIGHT-HAND RULE • Your palm faces in the direction of the force acting on the wire (p. 688).