WHAT IS MAGNETIC FIELD (B)? APPLICATIONS OF MAGNETIC FORCE

Magnetic Field (B) Magnetism is a fundamental force of the Universe (like Fg or Fe) Magnetic fields are produced by moving charges (current) Magnetic fields are produced by magnets

SOLENOIDBAR MAGNET Current in the coiled wire of the solenoid creates a magnetic field.

Magnetic Force Magnetic Forces exist when two magnets interact with each other (OR when a magnet and moving charge interact with each other)

AURORA BOREALIS In the last century, it was thought that the ice crystals in the atmosphere reflected sunlight resulting in the Aurora Borealis Angstrom used spectroscopy to show that there was a discontinuous spectrum of wavelengths – indicating that e- were being excited up to higher E levels, and then dropping down again (like Neon tube). The e-s are excited up by charged particles from the sun that enter the atmosphere at the magnetic poles!!!

VAN ALLEN BELTS AROUND EARTH

AURORA BOREALIS

MASS SPECTROMETER

Mass Spec. uses: Calculation of size and charge of atoms and mc. Determination of elemental components and structures of cmpds. Detection of trace toxins Carbon dating Calculation of the composition of plasmas and solar winds

LOUDSPEAKER

DOOR BELL Instead of an iron core in the electromagnet, there is a movable Iron plunger that strikes the bell.

When we speak of current direction The norm is to use “conventional” current From the positive to the negative terminal + _

Right Hand Rule for B Fields Thumb points in the direction of the current Curl fingers in the direction of the B field + OUT IN

Current Creates a Magnetic Field (B) I I I + I I I out

Magnetic Field Strength I + r 2r 3r B 1/2B 1/3B B = I μ o / 2πr μ 0 = a constant = 4π x T(m)/ A

Draw the following: 1.A current with a clockwise B field around it: 2.A current producing a B field directed straight out of the page: 3.A device which creates a B field from right to left: 4.A B field made by a square loop of wire: 5.A current flowing from right to left with a B field around it: 6.A current producing a B field directed out of the page:

The main points of Lab 18

When you turned the current on: A magnetic field was generated and the compass direction changed: B Earth (N) B solenoid (within) + I -

The direction of the compass

When you reversed the direction of the current The direction of the compass changed again to: B earth B solenoid (within) - +

Once again The compass shows us the net magnetic field due to B earth and B solenoid. Hey this is fun!!!!!

Then: You changed the direction of the solenoid so that the B solenoid was opposite B earth The compass needle would gradually turn toward the B solenoid as you increased the current (compass pointing S). Then you decreased the current so that the compass pointed ½ way between N and S. How much current did that take?

Like this: I B solenoid B earth

Then what? Knowing that the two fields are equal in magnitude and opposite in direction (given that specific current), you changed the orientation of the coil to be parallel to B earth once again – and kept the same current moving through the solenoid.

What happened????

Therefore: The two fields are equal in magnitude and adjacent to each other at a 45 O angle. The fields are vectors – and the net field is the net vector!!!

If you double the current: What angle do you think the compass needle will be deflected? B solenoid B earth

If you said: About 68 O N of B earth, I think you would have been correct.

As you can clearly see: B field vectors are additive But did you know that if you increase the # of turns of your solenoid, you increase the magnitude of the field generated? What variables do you think could have influenced your results in this activity? Great Job!!!!!