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GEOG/PHYS 182. Magnetic Field Measurement. Electromagnetism can be broken into two parts: Electric (We’ve studied) Magnetic (We’ll study today). Fundamental Forces: Gravity Electromagnetism Weak Strong (Nuclear). Electric Force (Coulomb Force) -Acts between electric charges (q)
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GEOG/PHYS 182 Magnetic Field Measurement
Electromagnetism can be broken into two parts: Electric (We’ve studied) Magnetic (We’ll study today) Fundamental Forces: Gravity Electromagnetism Weak Strong (Nuclear) Electric Force (Coulomb Force) -Acts between electric charges (q) -Charges can be positive or negative -Can be attractive (opposite charges) or repulsive (same type charges) -Universal gravitational constant: k = 8.99 ×109Nm2/C2
Electromagnetism can be broken into two parts: Electric (We’ve studied) Magnetic (We’ll study today) Fundamental Forces: Gravity Electromagnetism Weak Strong (Nuclear) At its surface, the magneticfield of the earth is ~0.5 G Magnetic fields -Produced by moving charges (electric currents) -Charges can feel forces when moving through a magnetic field… -Symbol: B (or sometimes H) -Units: T (tesla), G (gauss) where 1 T = 10,000 G
Magnetic Fields Magnetic fields are vector fields, meaning each point in space has: a magnitude (magnetic field strength); a direction in which the magnetic field points
All electric currents produce magnetic fields What is causing the electrons to move (current) in the circuit? You can determine the direction of the magnetic field lines bypointing your right thumb in the current direction and curlingyour fingers
Straight current-carrying wires: Wire loops and coils:
Magnetic Dipoles Dipole – As the names suggests has two poles Dipole – As the names suggests has two poles We’ve already discussed electric dipoles: -Charges +q and –q separated by a fixed distance d -The “poles” are actually the individual pointcharges A magnetic dipole consists of a north pole separated from a southpole
Forces on Magnetic Dipoles Magnetic dipoles experience a torque when placedin a magnetic field that attempts to align the north polewith the magnetic field-Design principle behind operating a compass! Iron filings can also be used to image magnetic fields (tiny compass needles)
Magnetic Dipole Electric Dipole Individual electric charges are also called electric monopoles Question: What happens when you break a bar magnet into two equal pieces? -Do you get a north pole in one hand and a south pole in the other? -From your experience, do magnetic monopoles exist in nature?
What does light have to do with any of this? Each of the four forces has a particle which is said to “carry” the interaction for that force The force carrier for the electromagnetic force is the photon
Magnets for Today’s Lab Bar Magnet Helmholtz Electromagnet