Blog 6: Magnetism and Electromagnetism

17.1

A magnetic field is the distribution of a magnetic force around a magnet.

• north and south are magnetic characteristics in electric fields
• similar poles repel (north and north or south and south)
• opposite poles attract (north and south)
• a test compass can be used to design a magnetic field
• the general direction is from the north end to the south
 




• 
  
  to test this out, you can sprinkle iron fillings around the magnet, which will form in a circular shape like shown above
• 
  
  Earth acts like a giant, permanent magnet which produces its own magnetic field

A Bunch of Terms

Ferromagnetic metals - metals such as iron, nickel, cobalt, or mixtures of these three that attract magnets.

Dipoles - small rotating magnets that make up large magnets.

 

Magnetic Induction - the ability of ferromagnetic materials to be magnetized

Demagnetization - loss of magnetic strength in a ferromagnetic material

Reverse magnetization - reversal of the polarity of a magnet

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Oersted's Principle states that charge moving through a conductor produces a circular magnetic field around the conductor



Blog 5: Resistance --- Ohm's Law

Section 16.5

Resistance is the measure of opposition to the flow of current

The amount of current flow in a circuit (amount of energy transferred) depends on two factors:

1. 
   
   The potential difference or voltage of the power supply, such as a battery.
2. 
   
   Natural path through the load.

Formula: R = V / I

• 
  
  R is resistance in Ohms (Ω)
• 
  
  V is the potential difference (V or Volts)
• 
  
  I is the current (A or Amperes)

• longer conductors have greater resistance
• thinner wires have greater resistance than thicker wires
• larger cross-sectional area means less resistance
• "resistance of 1Ω when 1A of current flows with a potential difference of 1V across a resistor"

Resistivity is the resistance of a substance (Units: Ω x m).

Gauge number of a wire indicates its cross-sectional area.

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Resistance in Series and Parallel Circuits

Section 16.6

Kirchhoff's current law states that "the total amount of current into a junction point of a circuit equals the total current that flows out of that same junction."


Kirchhoff's voltage law states that "the total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop."

• Kirchhoff's Voltage Law: V_T = V₁ + V₂+ V₃  
• Kirchhoff's Current Law:  I_T = I₁ = I₂ = I₃

 



  

Blog 4: Prelab- Using Voltmeter and Ammeter (Table)

Blog 3: Energy Ball Experiment and Circuits

           On Friday, the class received a new hands-on experiment: We were given "ping-pong balls" that could light up and hum; the balls could do these two things if the circuit was completed. 12 questions were given to us to complete:


1. Can you make the energy ball work? What do you think makes the ball flash and hum?
Everyone in the group was able to make the energy ball work by touching both of the metals on the ball. The ball flashes and hums because we were completing the circuit or creating a closed circuit, which allowed the electrons to move constantly.

2. Why do you have to touch both metal contacts to make the ball work?
Both metal contacts have to be touched by the same person to make the ball work because the circuit has to be closed in order for the electrons to flow. If two people touch one metal contact each without linking their bodies in any way, (such as touching fingers) the ball wouldn't flash and hum.

3. Will the ball light up if you connect the contacts with any other material?
As long as the metal contacts are connected with conductors or semi-conductors and are enclosed in a complete circuit, the ball will flash and hum. Our group tested this out by using a 2 metal balls, which worked and a plastic pen, which did not work.

4. Which materials will make the energy ball work?
As stated before, conductors and semi-conductors would make the energy ball work. Metals would work the best because they have low resistance qualities and have high levels of electrical conductivity.

5. This ball does not work on certain individuals. What could cause this to happen?
This ball does not work on individuals with skins that are not moist enough. Dry skin is a poor conductor of electricity.

6. Can the ball work with 5-6 people or the entire class?
The ball flashes and hums with our whole group and the entire class as long as everyone kept physical contact. (As long as everyone was touching each other's pinkies)

7. What kind of circuit can you form with one energy ball?

With one energy ball, we could form a series circuit.

A schematic of a series circuit

8. Give two balls, can you create a circuit where both balls light up?

Our group joined with another group to experiment this; when we made a complete circuit both balls lit up.

9. What do you think will happen if one person lets go of the other person's hand and why?

If one person lets go of the other person's hand, the balls wouldn't flash and hum because it is a broken circuit.

10. Does it matter who lets go?

If anyone let's go, the circuit is broken so the ball will not work. So it does not matter who lets go.

11. Can you create a circuit where only one ball lights up?

Yes, you can create a circuit where only one ball lights up by creating a parallel circuit. If a person lets go, the flow would still continue, leaving one ball to work.

12. What is the minimum number of people required to complete this?

This question was not worded clearly, so it was confusing. The minimum number of people required to accomplish this would be 1. Each finger (4 in total) touch each metal contact and this would create a parallel circuit.

                                    

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Series and Parallel Series

          

                There are two kinds of circuits: series and parallel. In a series circuit, loads (such as a light bulb) are placed in a single path, whereas in a parallel circuit, they are placed side by side. If any part of the series circuit is disconnected or not connected properly, the circuit will not work. If a path is broken, in a parallel series, the current will stop flowing through there and will flow through other paths. 

Blog 2: Newspaper Structure Challenge

Ready, set, go!!!

           On Wednesday, Mr. Chung gave us an exciting task to complete. The challenge was to construct the tallest structure with 5 sheets of newspaper and a limited amount of tape.


          Our group discussed what shape the base should be to ensure that the structure wouldn't topple to one side as well as how the following layers should be built up. We settled on creating a large triangular base, but we eventually ended up with a rectangular base because it was too hard. The following layers got smaller and smaller until it became a thin, rolled up sheet. At the very top of the structure, we taped a small piece of paper to increase the height. Our structure was unstable so we had to press in the newspaper at some points to alter the balance. About 20 minutes after, Mr. Chung told us to bring the structures to the front of the room to measure the heights. In the end, our group won by a centimetre!!!

  
          One of the best ways to create a strong, tall structure would be to have a triangular or rectangular pyramid as the base. Then, you would roll of the rest of the newspaper into cylinders and tape them vertically, one on top of another. Like our group, you could cut thin strips of paper in the beginning and add it on to the structure in the end.       

        

Blog 1: Notes on Current Electricity

1. Electrons in a static state have energy, but they are more effective when they transfer their energy.

2. Electric current is the flow of charge with a symbol I.

3. Current is the total amount of charge moving past a point in a conductor per time taken.
                     
                                                  Formula:        I   =  Q / T

4. An ammeter is a current-measuring device that must be wired so that all current flows through it.

5. In direct current, the current flows in a single direction from the power supply through the conductor to a load and back to the power supply. 

6. In alternating current, the electrons occasionally reverse the route of their flow.

7. A circuit is a path of current, which is needed for any electrical device to function properly.

A simple circuit with a load (light bulb), power source (battery).

8. Electric potential difference (V or Voltage) is the work done per unit charge as a charge is moved between two points in an electric field.

                            Formula:    V   =   E / Q   or   V   =  W / Q


9. A voltemeter is a device that can be used to measure potential difference.


10. An Ampere is a unit for current and the base unit is Coulombs(C) per second.