For this unit, my physics class discussed magnets and electromagnetic induction. We will be discussing magnetism (magnetic poles; electromagnets), forces on charged particles in an electric field (motors), electromagnetic induction, generators, and transformers.
Guiding Question- Why does a paperclip stick to a magnet?
Magnetism is surrounded by the common knowledge that all charges are magnetic and moving charges causes magnetism. Each electron is spinning in a domain. A domain is a cluster of electrons spinning in a random direction. When an object is magnetized all the domains line up in the same direction . All of the electrons run towards the north pole and run away from the south pole. These electrons eventually go through the north pole and come back around to the south pole. The movement of electrons are represented as lines and referred to as field line. The north pole of a magnet sticks to the south pol of another magnet because the field lines math up. The north pole of a magnet repels the north pole of another magnet because the field lines are opposite. If a magnet is cut in half, you you have a north side and a south side? The answer is no! You will just have two magnets now! Talk about saving you money. When referring to the paper clip question, it is important to realize that the paperclip has no set poles. The domains in the paperclip are random. A domain is a cluster of electrons that are spinning in the same direction. The magnet has a magnetic field. when the magnet is close to the paperclip the domains of the paperclip align to match the magnetic filed of the magnet. The paperclip now has a north and south pole. The north pole of the paperclip is attracted to the south pole of the magnet and thus the clip will stick to the magnet! We also discussed the northern lights and why they occur. The northern lights are caused by comic rays entering our atmosphere. Why do we only see these rays at the poles? The rays are noticed at the poles because when the magnetic field is parallel to a charged particle, the charged particle will not feel a force. When a particle is perpendicular to the magnetic field, it will feel a force and therefore bounce off. The rays feel a fore at the equator since the charged particle is parallel to the magnetic field of the earth. The northern lights enter at the poles because they are parallel to the magnetic field. This causes an increase in cancer at the poles since these rays contain cosmic radiation.
Guiding Question #2: What is needed to construct a motor?
Know we know that a charged particle feels a force form a magnetic field when it is perpendicular. This causes the particle to 'bounce off' and feel a force. We can apply this idea to a motor. A motor is used to transfer electrical energy, into mechanical energy. A motor is constructed from a battery, a rubber band, two paperclips, a coil of copper wire, and a magnet. The copper wire is made into a loop with two strands sticking out from either side. The copper wire is mounted over the magnet which is placed on the battery. The paper clips position the copper wire over the magnet and complete the circuit. The rubber band is used to hold the motor together. The main idea behind a motor is that a current carrying wire feels a force from the magnet. the magnet exerts a force on the copper wire since they are perpendicular. This causes the copper wire to torque. We could attach fan blades to make a fan or even wheels to make a car. The spinning wire, produces mechanical energy, capable of moving and object.
Guiding Question #3: How does a credit card work?
A credit card, traffic light, metal detector all work utilizing the ideology of electromagnetic induction. The basic idea surrounding this is a loop of wire in a complete circuit with no current has a magnet moved through or over the wire. This magnetic filed charges the wire and endues a current. The current can be used for a variety of things, If the magnet is constantly moved, changing the charge, a generator is created. A credit card contain a series of magnets in the black strip. There is a coil of wire in the credit card machine. As the credit card is moved through the machine, the magnets change the magnetic field within the loop of wire. This change in magnetic field endues a charge which is translated by the machine. The machine translates this signal into you credit card number. This answer an be adapted to answer how a traffic light detects a car, or how a metal detector detects metal. Pretty cool but we are not done yet!!
Guiding Question #4: What is the difference between a motor and a generator?
A generator has the same concept as the credit card machine in the previous question. A generator produces electricity by putting mechanical energy in. This is entirely different from a motor which transfers electrical energy into mechanical energy. The generator has a coil of wire and a magnet The magnet is either moved around the coil of wire or the coil of wire is moved around the magnet. A generator requires an ac current. The current need to be alternating or else the coil of wire will not feel a force. generators are used to power our homes during a power out. Normally the mechanical energy is either steam or wind, but can also be physical turning or fuel could be used.
Guiding Question #5: What is so special about transformers?
A transformer is used either increase the amount of voltage or decrease the amount of voltage in an appliance, Your computer has a small black or white box attached to the power cable. This transformer is used to convert the 120V in the wall into 300V in the appliance (these are made-up numbers). This increase in voltage is referred to as a step-up and commonly occurs for big appliances such as the washing machine or a microwave. A step-down transfer occurs when the energy is produced from the power company and transferred to your house. The power company makes the current very low and the voltage very high. This is done to reduce unnecessary power loss. if the current is very high, the power lines will heat up. Once the energy has reached your house it under goes a step-down. This occurs because in the transformer are two sets of wires. If we step down then the primary coils inside the transformer are larger than the secondary. If you want less voltage, then there will be less coils. We can calculate the number of coils in the primary or secondary or calculate the voltage in the primary or secondary. We use the formula;
Primary # of Coils/ Primary Voltage = Secondary # of Coils/ Secondary Voltage
For this unit, I found the motor section difficult to understand. During class we were explained that 'a current carrying wire feels a force from the magnet which causes it to torque.' I was always confused on what the force was that produced this torque but never fully understood. This topic, although appears difficult, needs to be taught in a specific order. I really enjoyed building the motor since it allowed me to have a visual and better understand the importance of every part. I hope that you build a motor!!
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