Tuesday, 28 February 2012

Right Hand Rule #2

The right hand rule #2 is used for coils.

It is used to determine the direction of magnetic field around a current-carrying wire and the conventional current flow.
When the coil is held with the right hand, the curved fingers point in the direction of conventional [positive (+)] current flow.

 


The thumb points in the direction of the magnetic field. The thumb also represents the north end of the electromagnet produced by the coil. 


Sunday, 26 February 2012

Earth As A Magnet

Planet Earth is a giant magnet and just like magnets, it has a magnetic field. The magnetism of the Earth caused by the Earth's iron containing core. The activities and the movements of the hot liquid metals inside the core create an electric current which produces the magnetic field. To simplify, we can visualize Earth as having a giant magnet bar inside it. The North end of the magnet bar points to the geographic South pole and the South end of the magnet bar points to the geographic North pole. But why? To understand better, we can look at how a compass works. 





A compass consists of a lightweight magnetised needle and one end of this needle always  points towards the North. This is based on the "opposites attract" rule (north and south attract, south and south repel). As a result, the north end of the magnet is attracted to the Arctic pole which is actually a 'magnetic North'. 


There is a difference between magnetic North and true North. True North which is at the North pole, is the geographical direction represented on maps and globes by lines of longitude. However, a compass does not direct you to the true North. The Earth's magnet is not aligned with the geographical poles and because of this, a compass points to the magnetic North. The difference between magnetic North and true (geographical) North is called the magnetic declination. 
Unlike the true North, magnetic North does not remain constant because of the changes in the Earth's magnetism caused by the movement of Earth's inner core. Therefore, for accurate directions, a GPS is preferred over a compass since it uses satellite signals instead of the Earth's magnetic field.   




References:


  1. Conger, C. (n.d.). Introduction to How to Find True North. HowStuffWorks "Adventure". Retrieved February 26, 2012, from http://adventure.howstuffworks.com/survival/wilderness/true-north.htm  
  2. Nowikow, I. (2001) Physics : Concepts and Connections. Toronto/Vancouver, Canada: Irwin Publishing.
  3. The Earth is a Magnet . (n.d.). The Earth is a Magnet. Retrieved February 26, 2012, from http://www.worsleyschool.net/science/files/magnet/earth/asamagnet.html





Saturday, 11 February 2012

The Energy Ball Report

1. The main difference in a series and parallel circuit is the connection of the loads. In a series circuit, there is only one pathway through which the current flows (5). In this circuit the loads (such as the energy ball in our experiment) are connected one after another in a series. As a result, if the path of the current is broken, all of the loads would no longer work. For instance, if one energy ball stops working or if the switch is open, the rest of the energy balls in the circuit would stop working as well. Here is a diagram of a series circuit:                                                              
                                                                    Series Circuit (3)

 In a parallel circuit, the loads are connected side by side. A parallel circuit has branches and each branch provides a separate path for the flow of the electric current (4). Therefore, if one load (energy ball) does not work, the loads on the other branches would still work.                           
                                                                   Parallel Circuit (3)

3. The human body consists of mostly water in addition to salts and minerals which is what makes our body a good conductor of electricity and conducts the current in the energy ball. This is why the energy ball works when we hold it with our hands. However, the energy ball does not work on some individuals. This is most probably because the individual is dehydrated and their body does not contain the sufficient amount of water containing minerals and ions to conduct the electricity (2). Also, under conditions where the skin is very dry, the energy ball might not work because the skin is lacking water to conduct the current (1).

Self Reflection:
 From this experiment, I have learned that I have good teamwork and collaboration skills. I worked well with my group and I tried to participate actively in group discussions and listened to everyone’s insights. When the group members are willing to participate in the group, I think that group work helps me learn better by trying to discuss my ideas with my group members and learning from their knowledge and insights. In addition, since I am a visual learner, hands on work helps me remember the concepts better. For instance, holding the energy ball and forming parallel and series circuits with the class helped me learn more effectively. However, I think I should work on my leadership skills because during the classroom activity of making parallel and series circuits, I did not take action arranging the class into the circuits. I should also work on my time management skills and try to not leave my assignments for the last day.

References:
(1)     Q & A: The Human Body Resistance | Department of Physics | University of Illinois at Urbana-Champaign. (2008). The Human Body's Resistance . Retrieved February 11, 2012, from http://van.physics.illinois.edu/qa/listing.php?id=6793
(2)     How is water a good conductor of electricity?. (n.d.). PhysLink.com - Physics and Astronomy Online Portal. Retrieved February 11, 2012, from http://www.physlink.com/Education/AskExperts/ae61.cfm
(3)     MGB Class - SCIENCE. (n.d.). Science in MGB. Retrieved February 11, 2012, from  http://kimberleyparkss.eq.edu.au/home/jmann30/science.html
(4)     Parallel Circuits. (n.d.). The Physics Classroom. Retrieved February 11, 2012, from    http://www.physicsclassroom.com/class/circuits/u9l4d.cfm
(5)  The Series Circuit. (n.d.). NDT Resource Center . Retrieved February 12, 2012, from http://www.ndt-ed.org/EducationResources/HighSchool/Electricity/seriescircuit.htm