Magnets and magnetic fields
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Intros
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Examples
Lessons
- Draw magnetic field lines of a bar magnet and horseshoe magnet.
- A compass is positioned at each of the following locations near a bar magnet. In which location the compass would point to the right-hand side of the page?
- Which of the following diagram best shows the magnetic field lines between the poles of two permanent magnets?
- Identify the magnetic poles labeled L and R in the diagram shown.
- Which of the following best represents the magnetic field between two magnets?
- Two identical bar magnet are placed as shown.
What is the direction of the magnetic field at point "P"?
Topic Notes
In this lesson, we will learn:
- Magnets and Magnetic Fields
- Erath’s Magnetic Filed
- Uniform Magnetic Field
Notes:
- Magnets attract objects made of iron such as paper clips and nails
- Any magnet (bar magnet or horseshoe magnet) has two ends or faces, called “poles”, the strongest magnetic effect.
- Compass is used for navigation; the needle of the compass is simply a bar magnet which is supported at its center of gravity to rotate freely.
- The pole that points the geographic north is called the "north pole" and another pole which points towards the geographic south is called the "south pole".
- Similar poles attract, opposite poles repel.
- If you split a magnet, you will not get isolated north and south poles; instead, two new magnets are produced, each with a north and a south pole.
- Ferromagnetic Materials: a type of material that shows strong magnetic effect such as, cobalt, nickel, gadolinium, and some of their oxides and alloys.
- Magnetic Filed: the region around the magnets and it represented by magnetic field lines such as;
- the direction of the magnetic field is tangent to a field line at any point
- the number of lines per unit area is proportional to the strength of the magnetic field.
- The direction of the magnetic field at a given point: it is defined as the direction that the north pole of a compass needle would point if placed at that point. The N pole of a nearby compass needle points away from the north pole of the magnet and points towards the south pole of the magnet.
- Magnetic field lines form closed loops, unlike electric field lines.
Erath’s Magnetic Filed - The Earth acts like a huge magnet; but its magnetic poles are not at the geographic poles, which are on the Earth rotational axis.
- Since the north pole (N) of the compass needle points north, the Earth's magnetic pole which is in the geographic north is magnetically a south pole.
Uniform Magnetic Field
- The simplest magnetic field is one that is uniform, it does not change in magnitude or direction.
- The magnetic field between two poles of a magnet is nearly uniform, except at the edges.
