10.1-11.1 presentations edited

EXAM RESULTS Average=73 Average = 64

Which one of the following statements concerning permanent magnets is false? A) The north pole of a permanent magnet is attracted to a south pole. B) All permanent magnets are surrounded by a magnetic field. C) The direction of a magnetic field is indicated by the north pole of a compass. D) Magnetic field lines outside a permanent magnet originate from the north pole and end on the south pole. E) When a permanent magnet is cut in half, one piece will be a north pole and one piece will be a south pole.

Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true? A) The magnetic force is a maximum if the particle is stationary. B) The magnetic force is zero if the particle moves perpendicular to the field. C) The magnetic force is a maximum if the particle moves parallel to the field. D) The magnetic force acts in the direction of motion for a positively charged particle. E) The magnetic force depends on the component of the particle's velocity that is perpendicular to the field.

Which one of the following statements best explains why a constant magnetic field can do no work on a moving charged particle? A) The magnetic field is conservative. B) The magnetic force is a velocity dependent force. C) The magnetic field is a vector and work is a scalar quantity. D) The magnetic force is always perpendicular to the velocity of the particle. E) The electric field associated with the particle cancels the effect of the magnetic field on the particle.

Forces on Charges

More Clickering … A charged particle enters a uniform magnetic field and follows the circular path shown in the drawing. The charge on the particle is: A Positive B Negative C Neutral D North E South

Look at the direction of the force and the velocity Magnetism

Magnetism

Magnetism

Off Angle P Magnetism

The Unit’s Experimental Set-up Force on a Wire

Use the VERTICAL setup as shown here. Change in Unit Plates are optional but you should try them.

Get To Work!

MM* *More Magnetism 10.2

The Magnetic Sector Mass Spectrometer Detector Array

An electrical current is flowing out of the page An electrical current is flowing out of the page. Looking INTO the current, the magnetic field is A Clockwise B Zero C Counterclockwise

A current carrying conductor is oriented as shown in the diagram. The FORCE on the wire with respect to the diagram is: A Left B Right C In D Out E Up or Down N S I

A current carrying conductor is oriented as shown in the diagram. The FORCE on the wire with respect to the diagram is: A Left B Right C In D Out E Up or Down N S I v B

Two parallel wires have electric currents that are flowing in the same direction. The two wires will A Attract B Repel C Have no interaction

Force on a Wire Carrying a Current in a B Field

Magnetic field of long straight conductor – Magnetism Placed over a compass, the wire would cause the compass needle to deflect. This was the classic demonstration done by Oersted as he demonstrated the effect.

Result r The permeability constant (μ0), also known as the magnetic constant or the permeability of free space, is a measure of the amount of resistance encountered when forming a magnetic field in a classical vacuum. The magnetic constant has the exact (defined) value µ0 = 4π×10−7 ≈ 1.2566370614...×10−6 H·m−1 or N·A−2). Magnetism

Force Between Two Current Carrying Conductors Magnetism First wire produces a magnetic field at the second wire position. The second wire therefore feels a force = Bil

Two Wires Magnetism

Today’s Experiment

Change in Unit The Experiment Plates are optional but you should try them.

Get to Work

How about a QUIZ???

Still More Magnetism L-10.3

The Quiz 2 r=a 1 Current out

Klicquer Question PHYSICS Points A, B and C form an equilateral triangle. Two parallel wires at B and C carry equal currents into the page. As a result of these two currents, what is the DIRECTION of the magnetic field at point A? A To the right B To the Left C Down D Up E In or out of the plane of ABC x  A C B

Discussion PHYSICS x  A C B A - Right

Kratos Profile HV-3 Gas Chromatograph & Direct Probe Mass Spectrometer Description Medium resolution double focusing (E/B) magnetic sector mass spectrometer with gas chromatograph and direct probe inlets; electron impact and chemical ionization sources.

EXAMPLE: Molecular structure and mass spectrum of 1-acetyl-4-(2-pyridyl)piperazine. The mass spectrum was obtained with a Perkin-Elmer ion trap detector.

Last Time – Force on a Wire

Let’s talk about torque Current Loops in Magnetic Fields

Current Loop What is force on the ends?? Loop will tend to rotate due to the torque the field applies to the loop. Magnetism

The Loop (From the top) OBSERVATION Force on Side 2 is out of the paper and that on the opposite side is into the paper. No net force tending to rotate the loop due to either of these forces. The net force on the loop is also zero, pivot Magnetism

The other sides t1=F1 (b/2)Sin(q) =(B i a) x (b/2)Sin(q) total torque on the loop is: 2t1 Total torque: t=(iaB) bSin(q) =iABSin(q) (A=Area) Magnetism

For a Coil of N Turns t=N(iaB) bSin(q) =NiABSin(q) DEFINE Magnetic Moment m:

Galvanometer This is a very sensitive instrument and is easily damaged.

Another Application: The motor If the conductor is a loop, the torque can create an electric motor.

What were your results last time? was f~bil?? Last Unit:

To Work

Coils and Lentz The Old and the New Magnetism 11.1

What the heck are we doing this week? 1 We will complete the chapter 2 We will look at Evil Lentz 3 We will complete the current and the next unit! 4 There will be a Friday Quiz

Transitions

Coils Company Logo www.themegallery.com

The Magnetic Field in a Coil S N Yikes … it’s a magnet!!!

What Do We do here??? The field inside the coil is just N times the field from a single coil. The field obtained by adding the fields from each coil separately. Don’t know how, though. The field cannot be calculated with the tools we currently have. The field is just another way to reduce our grades!!

Ampere to the Rescue! (1775-1836)   Ampere’s Law

B=0 l

We will now enter The Strange World of Dr. Lentz

We will now enter The Strange World of Dr. Lentz Gauss 1777-1955

Lentz’s Law

INDUCTION The movement of the magnet closer to the coil increases the “amount of magnetic field” going through the coil. This causes a current to develop in the coil. This process is called INDUCTION.

“Amount of Magnetic Field” needs to be defined: Magnetic Flux

GENERAL EXPRESSION FOR MAGNETIC FLUX

May the flux be with you

GRAPHICAL INTERPRETATION OF MAGNETIC FLUX The magnetic flux is proportional to the number of field lines that pass through a surface.

Induction 4/21/2017

The Magnetic Flux Going Through The Loop: Add up all of these pieces that are INSIDE the loop.

A triangular loop of sides 3,4 and 5 meters is placed perpendicular to a magnetic field B. The magnetic Flux through the loop is: A 12B B 6B C 3B D 20B E Not enough information is provided

Gauss’s law When you change the flux through a conducting loop, the CURRENT induced into the loop by this change will flow in such a way to create a flux change that opposes the changing flux that is causing the current in the first place!

Changing F Change any or all of the And the Flux will change! Bi DAi fi Change the SHAPE of the loop Change the ANGLE that the loop makes with the magnetic field (subset of above) And the Flux will change!

Changing the flux through the loop will change the current Changing the flux through the loop will change the current. But what way will the current actually flow?

which way will the current actually flow? Answer: The way that you don’t want it to!

Example of Nasty Lenz

today … something new

You worked on this unit last time. lets look at the end of the unit… + Handout Don’t calculate the current … just the direction of the current and explain to the class!

WORK ……. let’s do it! Finish unit and start the next one!