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Magnetism

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Question 1 0:16
  • Question 2 0:31
  • Question 3 0:56
  • Question 4 1:19
  • Question 5 1:35
  • Question 6 2:36
  • Question 7 3:03

Transcription: Magnetism

Hi everyone and welcome back to Educator.com. 0000

In this mini-lesson, we are going to talk about magnetism and what we are going to do is go through the first page of the APlusPhysics worksheet on magnetism, which you can find through the link down below the video. 0002

So with that, let us dive into question number 1. 0014

In order to produce a magnetic field, an electric charge must be -- Well the charge must be moving in order to create a magnetic field. 0017

The charge by itself without moving would create just an electric field. It has to move to get a magnetic field. 0024

Number 2 -- The diagram below shows a bar magnet. What is the direction of a compass needle placed at point (A)?0031

Well, the magnetic field goes from North to South outside the magnet, so the magnetic field would look like this and remember that a compass lines up with a net magnetic field, so if we put a compass at (A), it is going to go in the same direction as the net magnetic field or to the right. 0038

The diagram below shows a magnetic field near point (P).0057

If a compass is placed at point (P) in the same plane as the magnetic field, which arrow represents the direction of the North end of the compass needle will point? 0060

Well, that is going to again line up with the net magnetic field, which is going to be up and to the right, so our correct answer must be Number 2. 0069

Number 4 -- Which type of field is present near a moving electric charge? 0079

Well, moving charges create magnetic fields and because it is a charge, it already has an electric field, so we are looking for an answer with both an electric field and a magnetic field -- Number 3. 0083

Number 5 -- A student is given two pieces of iron and told to determine if one or both of the pieces are magnets. 0096

First the student touches the end of one piece to one end of the other and the two pieces of iron attract.0102

Right away, we know at least one is a magnet, otherwise they would not attract. 0107

Now the other one could be just a piece of metal that is attractable by the magnet or it could be a magnet as well. 0114

Next the student reverses the ends of the pieces and again touches the ends together. 0120

The two pieces attract again. 0124

Well if they were both magnets and they attracted one way, when you flip it around they should repel, so they both cannot be magnets. 0127

What this tells me is that one is a magnet and the one is a magnetic attractable, we will call it. 0132

What does the student definitely know about the initial magnetic properties of the two pieces of iron? 0143

And we figured that out going through the problem. 0148

One must be a magnet, the other must be a magnetic attractable. 0151

Number 6 -- The diagram below represents a wire conductor (rs) positioned perpendicular to a uniform magnetic field directed into the page. 0156

Describe the direction in which the wire can be moved to produce the maximum potential difference across its ends (RNS). 0165

Well, to do that, the easiest thing in my mind would be to have it moving left or right, crossing through those magnetic field lines to get the greatest induced current.0171

Last one, Number 7 -- The diagram below shows the lines of magnetic force between two North magnetic poles. 0184

At which point the magnetic field strength greatest? 0191

Well, remember magnetic field lines show the direction of the magnetic field and where they are most dense you have the strongest magnetic field and where they are least dense you have the weakest magnetic field. 0194

So where are the lines most dense? Right there around (B). Correct answer is Number 2. 0204

Hopefully, these went very well. If they did you are ready to move on and go to AP level questions. 0211

If they did not go so well, it is probably time to go back and review the lesson on magnetism. 0216

Thanks so much for your time everyone and make it a great day.0221