Chapter 9 Review Questions Essay

Electricity is the flow of electrons through a metal wire, or through a conductor. Electrons are tiny particles found in atoms, and is also one of the building blocks of all matter. Electrons carry tiny negative charges, when they move through a conductor they produce a little invisible magnetic force. The strength depends on how in motion the electrons are. Pushing the electrons a little closer and tighter can cause a stronger field. When electrons produce a magnet force, you can use a magnet to make the electrons mover which is how an hydroelectric generator works.

Bill Nye Resources on Magnets and Magnetism: http://billnye.com/billnye_resource/magnetism/ (Links to an external site.)Links to an external site. and https://vimeo.com/121217374 (Links to an external site.)Links to an external site.

A magnet is an object with a magnetic field. A magnet appeals to any object containing iron. These objects are considered ferrous objects and may include pieces of iron, cobalt, nickel, and steel. The end of a magnet will always point in either the North or South direction. The end that points north is called the North Pole and the end that points south is called the South Pole. It

One aspect that is understood, however, are the effect magnetic fields have on our bodies during everyday life. We are constantly being exposed to magnetic fields. Microwaves, power lines, radio waves, refrigerators: these all give off magnetic charges (CSA, 1994; Barnothy p. 123). The earth is surrounded by a magnetic field, which is the reason for the North and South poles (Leonard, 861).

Human civilisation has dealt with magnetism for millennia, earliest evidence dating as far back as 1000 BC where the ancient Chinese civilisation discovered a naturally occurring magnetic ore, magnetite. This ore, commonly known as lodestone was used by the ancient Chinese as a geomagnetic compass, however, no one really knew what magnetism was at the time. For centuries on, we have had basic knowledge regarding electricity based upon static electricity found from rubbing amber and fur. However, up until the early 1800s, our understanding of electricity and magnetism was severely limited – considering both of them as entirely separate phenomena.

Bar magnet is the simplest form to explain magnetism. Bar magnets are permanent magnets and this means that they have magnetism all the time, it can’t be turned on and it can’t be switched off. They have two poles that include: north-seeking pole (N) and south-seeking pole (S). These poles appear to occur in equal and opposite pair. Magnetic meridian is the vertical plane in which the magnet lies. Magnets are made of materials that can be magnetized, which are also the ones that can be attracted to magnet, which are called ferromagnetic materials. These include: iron, steel, nickel, cobalt, some alloys of rare earth metals and some naturally occurring minerals such as lodestone. Mu-metal is a nickel based soft magnetic alloy,

The state and behavior of a magnetic material is recognized by the directional sum of its magnetic moments. Without the influence of an external magnetic field, the cross’s magnetic moments produce a neutral directional sum, indicating that the cross is not attracted in any one direction. Once the lifting magnet is engaged however, the direction of the moment sum shifts towards the lifting magnet, indicating that the cross is attracted to the magnet.

The characteristic of a series wound DC motor is that its speed is proportional to the load and as there is a lower load it has an increase in speed. Also the torque allows for moving of large loads allowing it to be

Magnet - creates a magnetic field. The stronger it is the higher efficiency and accuracy of a speaker. It is worth noting that nowadays this is a permanent magnet as opposed to the earliest designs which used electromagnets. The most common and cheapest material used is ferrite but the most effective are alnico magnets (consist of aluminium–nickel–cobalt hence the name).

The objective of the experiment was to understand the North and South poles of a magnet and how they relate to each other for a single magnet and two magnets when like poles or unlike poles are placed together. The results of the experiments verified the properties of magnets with respect to how like poles repel and how unlike poles attract. Also, electromagnets were created and investigations confirmed Lenz’s law. The experiment produced results that agreed with expectations, confirming the behavior of like poles, unlike poles, electromagnets and Lenz’s law. A Magnetic Field Sensor was used to measure the magnetic field due to the current flowing in the coil and showed a steady magnetic field relative to time.

Brushless DC motors is a kind of permanent magnate synchronous motor. Permanent magnet synchronous motors are classified on the basis of the wave shape of their induce emf, i.e, sinusoidal and trapezoidal. The sinusoidal type is known as permanent magnet synchronous motor (PMSM); the trapezoidal type goes under the name of PM Brushless dc (BLDC) machine. Table (2.1) shows the difference between (PMSM) and (BLDC) motor.

Induction machines are classified into two which includes motors and generators. The basic principles of these motors can be applied and hence develop equations describing its behaviour. The most common motors include squirrel-cage, wound-rotor ranging from few horsepower to thousands as the case may be. Squirrel Cage Rotor consist of a bare copper, slightly longer than the rotor, while a wound rotor has a 3 phase windings, and are evenly distributed in the slots, usually connected in 3-wye. The resistors are mainly used during the start-up period under normal running conditions.

Figure One. (a) The internal arrangement of the coils for a bipolar stepper motor. (b) The internal arrangement of the coils for a unipolar stepper motor. Wires a through d are

RC2 is open to ensure that the forward coil cannot be activated when the motor is running in the reverse direction. RC1 is closed to ensure that the motor keeps running even when the start button return to its normal position.

3) The piston now moves up from bottom dead center to top dead center, effectively ending a cycle and starting another. The spark plug