1 / 12

Magnetism and Electricity

Magnetism and Electricity. Chapter 13. Reminders. Lab this week due by Friday at 4:00 pm: B3-CLE: Coulomb’s Law of Electrostatics Reading quiz due prior to the start of class on Thursday. Test #3 (Chapters 8, 9, 11-13) on Thursday, April 10 th

dolf
Download Presentation

Magnetism and Electricity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Magnetism and Electricity Chapter 13

  2. Reminders • Lab this week due by Friday at 4:00 pm: B3-CLE: Coulomb’s Law of Electrostatics • Reading quiz due prior to the start of class on Thursday. • Test #3 (Chapters 8, 9, 11-13) on Thursday, April 10th • Deadline to Car Crash Reconstruction optional extra credit problem due Thursday, May 1st

  3. Compasses and Lodestones • Magnetic compass known from ancient times • Chinese probably the first (Marco Polo reported) • Compass needle prepared from lodestone • Needles float on water • Compasses have “north” and “south” ends • Like poles repel – opposites attract. • Magnetic monopoles do not exist.

  4. Earth’s Magnetic Field • Earth acts as though there is a large bar magnet at its center – with its south magnetic pole ~4o from Earth’s north geographic pole.

  5. On the Move and Weakening! • The “north” end of the compass points to the south magnetic pole of the Earth • The magnetic south pole is located north of Canada and is on the move! • Strength is currently decreasing at a rate of about 6.3% per century.

  6. Fields in Physics 1 • A field is a hypothetical construct designed to explain action at a distance. • Two types of forces: • Contact forces • Pushing and pulling • Action-at-a-distance forces • Gravitational force • Electrical force • Magnetic force • Certain nuclear forces (weak and strong)

  7. Fields in Physics 2 • Gravitational: • Arrows indicate direction of motion of any matter. • Always attractive on a “small” scale • Electrical: • Arrows indicate direction of motion of a positive test particle, p+ (a proton) • Opposites attract; likes repel • Magnetic: • Arrows indicate direction of motion of a north “monopole” which DNE. • Opposites attract; likes repel

  8. Fields in Physics 3 • The concentration of field lines indicate field strength (measured in N/kg, N/C, or Tesla) • The closer lines are, the more intense the field. • The more intense the field, the stronger the attractive or repulsive force. • When field lines point in the same direction, this indicates attraction and visa versa.

  9. Magnetism from Electricity • Öersted shows that direct (one way) flowing electricity produces a constant magnetic field. • Ampère shows that parallel current carrying wires have an attractive force between them. • Ampère argues that currents flowing within the Earth are responsible for the planet’s magnetic field.

  10. Faraday’s Lines of Force • Field lines trace out magnetic fields. • Magnetic fields are directed from N to S. • A long, current-carrying wire produces a circular field consistent with the right hand rule #1. • Magnetic fields of currents – the solenoid. Current is defined to flow in the same direction as a positive (+) test particle.

  11. F on a Charge as a Result of B, v • Charged particles (+ and –) moving in a magnetic field experiences a force, F, but only so long as v is not parallel to B. • The direction of the force is given by right hand rule #2. Current is defined to flow in the same direction as a positive (+) test particle.

  12. Electricity from ChangingB Field • Faraday discovers electric induction. • Today we have the electric generator. • Charges in the presence of a changing magnetic field are forced to flow in conducting wires. • Faraday’s law – The strength of an electromotive force induced in a loop of wire is proportional to the rate at which the magnetic flux through the area of the loop changes. • AC is used in preference to DC current.

More Related