Thursday, May 28, 2009

Thursday, May 28, 2009

Physics Extravaganza wrap-up form

Asked students what they knew or remembered about magnetism. Very few answers.

Talked about magnetism of earth.
Force law, right hand rule
Students tried quiz problems.

Students worked on Magnetic problem worksheets

Wednesday, May 27, 2009

Prepare for Physics Extravaganza.

Many students just sat around and chatted. Some worked hard on their demos.

Tuesday, May 26, 2009

Tuesday, May 26, 2009

Go over electricity test.

Prepare for Physics Extravaganza

Friday, May 22, 2009

Friday, May 22, 2009

Test on Electricity
No homework over 3 day weekend

Thursday, May 21, 2009

Students had time in class to work on problems in preparation for tomorrow's test.

Wednesday, May 20, 2009

Students did meters lab. Handed in report.

Tuesday, May 19, 2009

Students redid circuit exercise lab after I went over results.

Monday, May 18, 2009

Students did circuit exercise lab

Friday, May 15, 2009

Students did electrical measurements lab.

Thursday, May 14, 2009

Did Physiological Effects of Current Lab.

Didn't take as long as expected.

Wednesday, May 13, 2009

Went over electrostatics test.

Students doing IB Physics came to class after finishing paper 3 of the exam. Gave them blank copies of the electrostatics as I went over it.

Tuesday, May 12, 2009

IB Physics students gone for first day of testing.

Students not testing in IB Physics took electrostatics test.

Monday, May 11, 2009

Monday, May 11, 2009

Day before first IB test.
Answered questions from IB practice test.
Showed Powerpoint on Digital Technology.

For those not taking IB test tomorrow, test on electrostatics.

Friday, May 8, 2009

Out sick.

Students were asked to look through IB textbooks and review sections on digital technology and photoelectric effect.

Thursday, May 7, 2009

Out sick.

Students could check answers to magnetism worksheets.

Watch powerpoint on Climate Change and file on atomic physics

Wednesday May 6, 2009

Covered Lenz's Law and electromagnetic induction.

Went home sick after this class

Tuesday, May 5, 2009

Reviewed magnetism from Monday.
Showed generator and motor.

Went over several applications of magnetism including parallel conducting wires, Hall Effect, oscilloscope, mass spectrometer.

Monday, May 4, 2009

Monday, May 4, 2009

Reviewed concepts from electricity for those students who missed Friday's class due to IB testing.

Reviewed formula for resistance: R = resistivity * length/Area
Resistivity is temperature dependent. In general, the lower the temperature, the lower the resistivity. Superconductors occur at very low temperatures.
Reviewed Ohm's Law
Reviewed resistors in series and parallel. Derived the equations for finding equivalent resistance. Showed how to do a complicated problem.

Reviewed using voltmeters and ammeters in circuits.
To use an ammeter, you break the circuit and insert the ammeter to measure the current. Ammeters are connected in series. Ammeters must have low internal resistance to not change the resistance of the circuit.
Voltmeters measure potential difference across a circuit element or between points in a circuit. Voltmeters must have high internal resistance so as not to increase the resistance of the circuit.

Meters and power supplies have internal resistance. If you connect a voltmeter across a battery, it may read the EMF because the current is very low and you do not get much of a voltage drop across the internal resistance. In a circuit, the current may be greater and you will have a voltage drop across the internal resistance decreasing the output voltage.

Did some problem on request from the second electricity worksheet.

Started magnetism.
Four forces. Magnetism has now been combined with electricity.
Currents create magnetic fields.
Changing magnetic fields create currents.

Demonstrated producing current in a coil by relative motion of a magnet and the coil.
Demonstrated magnetic field lines with iron filings.

Magnets have two poles, north and south. Opposite poles attract.
Discussed magnetism of Earth and that the geographic north is magnetic south since the north end of the compass needle points north and opposite poles attract.
Showed maps of magnetic declination.

Used right hand rule to find electric field lines around a current carrying wire. Intensity of the field is given by B = uo I/2 pi r
Force on a moving charge is given by F = qv X B where X is the vector cross product.
You cannot do magnetism in two dimensions, unlike the electric field where F = qE and the force and electric field are co-linear.

If v and B are perpendicular, then F = q v B. If v and B are co-linear, then F = 0.
Showed how to use the right hand rule to find the direction of the force.

Worked problem of parallel current carrying wires and showed that if the currents are in the same direction the wires attract and if in opposite directions they repel. Measuring the force of attraction gives the definition of the ampere.

Quiz on direction of magnetic fields around a current carrying wire.
Handed out both worksheets on magnetism.

Friday, May 1, 2009

Thursday, April 30, 2009

Wednesday, April 30, 2009

Tuesday, April 28, 2009