Presentation on theme: " Electric generators Television sets Cathode-ray displays Computer hard drives Compass."— Presentation transcript:
Electric generators Television sets Cathode-ray displays Computer hard drives Compass
Polarized-magnets are polarized. They have two distinct and opposite ends. North pole and South pole Like electric charges, likes repel and opposites attract However, charges can be separated magnetic poles cannot.
The Earth itself is a large magnet. The north end of a compass needle (a magnet) points to the geographic north pole. The geographic north pole is the magnetic south pole
A magnet can cause another metal to become polarized and have magnet properties.
Because of the microscopic nature of the material it keeps the magnetic properties ALNICO V-a permanent magnet alloy aluminum, nickel, and cobalt Rare earth elements neodymium and gadolinium produce very strong permanent magnets for their size
Magnetic forces can be describe by the existence of a field around the magnet Much like gravitational and electric fields Can be non-contact forces Magnetic fields are vector quantities that exist in a region in space where a magnetic force occurs.
Magnetic field lines are imaginary lines used to help visualize a magnetic field. Direction of field lines are defined as the direction that a compass points when placed in the magnetic field. Outside the magnet field lines leave the magnet from the north pole and end the south Inside the magnet from south to north to form a closed loop.
The number of field lines passing through a surface is the magnetic flux The flux per unit area is proportional to the strength of the magnetic field.
In 1820, Danish physicist Hans Christian Oersted experimented with electric currents in wires. Found that when a current was in a wire a compass needle rotated until it was perpendicular to the wire. If the compass needle rotated it must have been because of a magnetic field.
Circular line indicate that magnetic field lines around a current carrying wire for closed loop in the same way that field lines about a permanent magnet for closed loops.
A method to determine the direction of a magnetic field relative to the direction of conventional current Pretend to hold the wire with your right hand Point you thumb in the direction of conventional current Your fingers point in the direction of the magnetic field.
A long coil of wire consisting of many loops is called a solenoid. The field of each loop adds to the fields of the other loops and creates a greater total field strength.
A method used to determine the direction of the field produced by an electromagnet relative to the flow of conventional current. Curl your right hand fingers around the loops in the direction of the conventional current Your thumb points toward the north pole of the electromagnet
Electrons in an atom acts like a tiny electromagnet Domain is when the magnetic fields of the electrons in a group of neighboring atoms are all aligned in the same direction When a piece of iron is not in a magnetic field the domains point in random directions and their magnetic fields cancel each other out.
In the case of a temporary magnetic and external magnetic field aligns the domains and when the external magnetic field is removed the domains return to their random arrangement In a permanent magnet the iron keeps the domains aligned after the external magnet is removed.