Definition
Describe the results of the Oersted experiment
Oersted found that, for a straight wire carrying a steady (DC) current:
- The magnetic field lines encircle the current-carrying wire
- The magnetic field lines lie in a plane perpendicular to the wire
- If the direction of the current is reversed, the direction of the magnetic force reverses.
- The strength of the field is directly proportional to the magnitude of the current.
- The strength of the field at any point is inversely proportional to the distance of the point from the wire.
Definition
Effect of Current on a Compass Needle
Compass needle is a magnetic needle , so when placed still will align itself in north-south direction, if we bring a bar magnet near the compass the needle will deflect based on the property that like poles of two magnets repel each other. As soon as the other magnet is removed,the magnetic needle will come back to its original position.
This same thing happens when a current carrying circuit is placed near a compass. As soon as the key is closed current will pass through the coiled wire shown in the figure and it will start behaving as a electromagnet and will deflect the needle and when the key is made open the magnetic needle will again point to north-south direction.
This same thing happens when a current carrying circuit is placed near a compass. As soon as the key is closed current will pass through the coiled wire shown in the figure and it will start behaving as a electromagnet and will deflect the needle and when the key is made open the magnetic needle will again point to north-south direction.
Definition
Magnetic domain
A magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual magnetic moments of the atoms are aligned with one another and they point in the same direction. When cooled below a temperature called the curie temperature
Definition
Weber's Theory of Magnetism
A popular theory of magnetism considers the molecular alignment of the material. This is known as Weber's theory.
This theory assumes that all magnetic substances are composed of tiny molecular magnets. Any un magnetized material has the magnetic forces of its molecular magnets neutralized by adjacent molecular magnets, thereby eliminating any magnetic effect.
A magnetized material will have most of its molecular magnets lined up so that the north pole of each molecule points in one direction, and the south pole faces the opposite direction. A material with its molecules thus aligned will then have one effective north pole, and one effective south pole.
An illustration of Weber's Theory is shown in fig., where a steel bar is magnetized by stroking. When a steel bar is stroked several times in the same direction by a magnet, the magnetic force from the north pole of the magnet causes the molecules to align themselves
This theory assumes that all magnetic substances are composed of tiny molecular magnets. Any un magnetized material has the magnetic forces of its molecular magnets neutralized by adjacent molecular magnets, thereby eliminating any magnetic effect.
A magnetized material will have most of its molecular magnets lined up so that the north pole of each molecule points in one direction, and the south pole faces the opposite direction. A material with its molecules thus aligned will then have one effective north pole, and one effective south pole.
An illustration of Weber's Theory is shown in fig., where a steel bar is magnetized by stroking. When a steel bar is stroked several times in the same direction by a magnet, the magnetic force from the north pole of the magnet causes the molecules to align themselves
Definition
Permanent Magnet
A good permanent magnet should produce a high magnetic field with a low mass, and should be stable against the influences which would demagnetize it.
Definition
Permanent and Temporary magnets
| Permanent Magnets | Temporary Magnets |
| A permanent magnet is one that retains its magnetic properties for a long period of time. Examples are iron, nickel, cobalt and some rare earth alloys etc. | Temporary magnets are those that simply act like permanent magnets when they are within a strong magnetic field. Unlike permanent magnets however, they loose their magnetism when the field disappears. Paperclips, iron nails and other similar items are examples of temporary magnets. |
Definition
Magnetic field
The region or space around a magnet, within which its influence can be experienced is called magnetic field of that filed.
Definition
Intensity of Magnetic field
The intensity of magnetic field at a point in a magnetic field is defined as the force experienced by unit north pole when placed at that point.
Definition
Magnetic field
The region surrounding the magnet, in which the force of the magnet can be experienced, is called magnetic field.
Definition
Arrangement of iron fillings around a bar magnet
When iron filings are placed in magnetic field, they are magnetized and induce poles in them. Hence, they act as small magnets themselves. These filings orient themselves along the magnetic field lines of the bar magnet as shown in the figure.
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