IB Physics 12 Mr. Jean December 4 th, 2013

The plan: Video clip of the day – 123 (moose) 123 Internal Resistance of a battery Unit Analysis of Tesla –Notes from Last Day Ampere’s Law Lenz’s Law Solenoids

To note: Upon reviewing the notes I noticed that we missed the “Internal Resistance of a Battery” formula. This was scheduled to happen the same day as the Unity Charity event and I only realized it missing today.

Internal Resistance: Systems do not like to change when in steady state. When a battery is not connected it’s at a steady state; however when we start get current to flow we need to push the current down the wire. In a closed circuit we see that the wire is connected back to the battery. Thus the current must go back through the battery. Therefore because it takes some energy to more the current even a battery has resistance.

Internal Resistance:

E = I (R + r)IB Notation: E = EMF I = Current in the system R = Resistance in system r = Resistance in the battery

Internal Resistance: ow0http:// ow0

Basic principle of electromagnetic induction: –whenever the magnetic field in the region of a conductor is moving or changing in magnitude, electrons are induced to flow through the conductor.

When the magnetic field through the coil changes, a current flows as if there were a power source. –aka: EMF (electromotive force) in the circuit.

Unit Analysis for Tesla: A particle carrying a charge of 1 coulomb and passing through a magnetic field of 1 tesla at a speed of 1 meter per second perpendicular to said field experiences a force with magnitude 1 newton, according to the Lorentz force law. As an SI derived unit, the tesla can also be expressed as Units used: –A = ampereampere –C = coulombcoulomb –kg = kilogramkilogram –m = metermeter –N = newtonnewton –s = secondsecond –T = tesla –V = voltvolt –Wb = weberweber

Ampere’s Law: –Magnetic field’s circulation is proportional to the amount of current being pushed through the wire. –We use the first right hand rule to show the direction of the current as well as the field. Brightstorm: –

Lenz’s Law:

Faraday / Lenz’s Law: Brightstorm: Faraday Lenz’s Law – 42Ihttp:// 42I

Electro-magnetic Induction: Brightstorm: Electro Magnetic Induction: – bqIhttp:// bqI

To do: Work on complex circuits Tomorrow’s class –AC & DC electric engines