Lessons 5 & 6 Notes Magnetic Force The Earth’s Magnetic Force

Magnetic Force (L5) Magnets have a north pole and a south pole. 2 like poles will repel. – The north pole of one magnet will repel (pull away) from the north pole of another magnet. – South pole and south pole will also repel. 2 opposite poles will attract. – North pole and south pole will attract (push towards).

The force of interaction between 2 magnets depends on the distance between them. – The closer 2 poles are to one another, the stronger the force. – The farther away 2 poles are from one another, the force decreases. The space around a magnet is described as a magnetic field because magnets can influence objects without touching them.

Types of Magnets Flexible magnets (small black rectangles). – Made of rubber/plastic, but contain many tiny particles of iron or ferrite. – One flat side is the north pole and the other flat side is the south pole. Bar magnets (permanent magnets). One end is the north pole and the other end is the south pole. – The suspended bar magnet aligned itself with “magnetic north”. Lodestone – pale brown to black rock that contains a lot of magnetite, a black magnetic material.

The Earth’s Magnetic Force (L6) The magnetic field of the Earth is believed to be generated by the molten core that rotates with the Earth. The Earth’s magnetic field is similar to that of a bar magnet. There is a north pole and a south pole. Magnetic north is close to the geographic north pole and magnetic south is close to the geographic south pole. The earth’s magnetic field has undergone several reversals, but scientists have not been able to explain why.

A magnetic compass aligns itself so that it points to the magnetic poles of the earth because of earth’s magnetism. Any magnets near a magnetic compass can deflect the needle of the compass, giving an inaccurate reading.

Fair Test An experiment that keeps all things the same, except the thing you are trying to investigate. To design a fair test you need to: – Identify the independent and dependent variables – Identify the constants (controlled variables) The independent variable should be changed in a consistent manner. (Example: one magnet was added at a time.)

Each time the independent variable is changed, the dependent variable should be measured, and the controlled variables (constants) should be checked to make sure they have not changed during the procedure. Independent variable – number of magnets stuck together Dependent variable – number of washers Controlled variables (constants) – type of paper clip, tongue depressor (popsicle stick) used and in its placement on the cups, types of washers used.