Demonstration of Magneto Static Forces - Essay Example

?Experiment To Demonstrate Magneto Static Forces Aim: To show that Magnets can produce forces when placed across a space that is empty. Introduction Magneto static or dipole-dipole forces are very critical in determining the microstructure of any magnet. Magnetic fields in magneto statics which are constant at a particular moment in time always produces steady currents. The charge passing in a wire at per unit time is called the current of that particular wire. Conventionally, it is assumed that electric current always flow in the direction of the movement of the positive charges. The SI unit of current is Amperes (A) or coulombs-per-second. Materials and Equipment: bar magnet, plotting compasses, paperclips or dressmaker’s pins. Procedure Take a strong bar magnet and place it on an OHP. Then sprinkle dressmaker’s pins or paperclips. Record what happens. Plotting compasses were scattered around a magnet, then observe what happens. Observations It was observed that the paperclips or dressmaker’s pins clanged to the poles of the magnet. This shows that magnets have North and south poles that attracts magnetic materials, that is, the pins and paper clips strongly. Also the pins were deflected when plotting compasses were brought closer to the magnet but not touching it. This was due to the repulsion that was caused by a plotting compass since it behaves like a magnet of similar pole to the magnet on the table. This repulsion is what caused the dressmaker’s pins and paper clips to deflect Experiment 2a: To Identify A Magnetic Material Equipment and Materials: a) Three square plates of material; steel, aluminium and PVC (plastic). b) A pair of small neodymium magnets. One of the magnets is attached to a threaded stud. Procedure Bring steel closer to the magnet attached to the threaded stud and observe what happens. Repeat the experiment using aluminium and PVC (plastic) and note the behavior. Results: It was noted from the experiment that aluminium and steel get attracted by the magnet while no effect is felt using PVC. This clearly shows that both Aluminium and steel are magnetic material while PVC is a non-magnetic material. Can a non-magnetic conductor be used to ‘block’ or ‘shield’ a magnetic field? Yes. Nonmagnetic materials which are conductors can shield the magnetic field to some extent. Some non-magnetic materials which are conductors help shield magnetic field. A good example is a superconductor, when this material is placed between two magnetic materials; it tends to exclude the magnetic fields created by the magnets. A superconductor material behaves like a magnet in that if the South Pole of the magnet is brought near it, the magnet behaves as though it is being approached by itself from the other side the superconductor. The magnet’s South Pole then starts to repel the “north pole of the other magnet”, which is just a mirror of itself. Therefore, if a superconductor is placed between which are facing each other no change will be noticed since the two poles of the magnet will tend to repel each other hence cutting off the magnetic fields that existed before. This scenario is very useful in case you don’t need any field in a particular region. The iron box will be used since the fields travel in the walls of the box and does not penetrate into it. Falling magnets Using the three plates inclined at an angle of 60 degrees, place the magnet on the three plates and allow the magnets to slide from a height of about 30cm. the experiment is repeated by using copper pipes held vertically. The magnet without a stud is dropped while its axis of symmetry is vertically down each pipe. When the magnet is placed along the three plates inclined at an angle of 60 degrees, the magnet slide down the plate slowly. This happens so because the voltage will increase as the magnet moves down the sheets and not when magnet it is stationary. Magnetic fields come about due to electric currents. If these magnetic fields are changed by moving the magnet near a non-magnetic material or metal, it induces electric field that is the difference in voltage in the metal. This then produces a magnetic field which is oriented in the direction opposite to that of the magnet. As the magnets moves next to the metal it creates magnetic fields which act in a specified direction. These fields always try cancelling the magnetic field that is created in the metal since the metal doesn’t like harboring magnetic or electric inside them. The falling magnet is attracted by the fields that have been induced to the metal creating resistance. The resistance created is what actually slows down. As the speed of the magnet reduces, it ceases to generate more current hence this decreases the resistance on the magnet as it moves. Fig 1:Magnetic fields caused by repulsion of magnet The action of the gravity also comes to play as it speeds up the movement of the magnet until it reaches a medium speed. It is noted the magnet creates a whirlpool of electrons as it falls down the pipe around it. Fig2 magnetic field separated by a superconductor material Definition of Homopolar motor According to Webmaster, A homopolar motor can be defined as a moto whose magnetic field is along the axis on which the fields rotates and the electric current which are not parallel at a given point to the magnetic field. From the term homopolar, it implies that there is no polarity change (Homopolar Motors, 2003). How it is constructed A neodymium magnet is fixed to the top of a stud magnet. The stud, in turn, is magnetized as a result of the power or rather strength of the neodymium magnet. The pointed end of this stud is then fixed to the lower terminal of an AA size 1.5 V D-cell battery. This makes it to remain hanging freely as a result of gravity as the casing of the battery is made of ferromagnetic material and generates very little friction connecting between the battery and the loosely hanging magnet. Pressing one edge of the battery against the terminal of the battery using one’s finger and then brush the other edge of a wire against the rims of the magnet closes the circuit. This has the effect of causing the current to flow and in turn leads to the spinning of the disc for the magnet How homopolar motor works An electric current or rather moving electric charge in any magnetic field will encounter a force which is at right angles to the direction in which the current and the magnetic field moves. This force is called Lorentz force. This force was first described by Faraday in what he termed as electromagnetic rotation. For a homopolar motor, the battery produces electric current which then moves in a radial manner through the magnetic disc, this disc magnet has a magnetic field which is moving along its longitudinal axis. Lorentz force which is a resultant force in which is along tangential direction and produces a torque. The torque produced then rotates freely with the attached stud. The magnet need not be electrically conductive in order to move. The magnet can be attached on the battery, then the wire allowed to rotate in a free manner and in which case closes the circuit at the rotational axis. Additionally, at a point along the loop of of electricity, the magnetic field and the current in the wire are not parallel, at this point a Lorentz force occurs which is perpendicular to them. Lorentz force is always tangential at this point and tends to produce torque in the connecting wires, causing the wire rotate. Just like many electro-mechanical devices, a motor which homopolar is reversible in that when electric energy of any magnitude is placed on the terminals, the mechanical energy will be produced from motors motion and the reverse is true. Maximizing the number of coils in the electromagnet and pick up coil From Faraday's law of induction, if current passes in a circuit it induces voltage in the nearby circuit. For this set up, a very large solenoid field coil with maximum number of turns per meter was used to generate a time-varying magnetic field by passing an AC current (I1) through it. The AC current I1 passing through the field coil produces a time-varying magnetic field given by: (1) Where n is the turns density (turns/meter) of the coil. If the current I1 is sinusoidal and given by: (2) Then, the induced voltage, v, in the induction coil is given by: (3) Where a and N are the radius and the number of turns of the induction coil, respectively. From the experiment it is expected that the relationship between both the voltage and current ratio and the coil-turn ratio is close to linear. Despite this fact, the gradient of the resulting lines will not necessarily be equal to unity. Read More