How to Avoid an Electrical Kitchen Fire: A Simulation

Per Group - One item unless otherwise noted

• battery- 6 volt
• 6 Christmas tree lights with 3 inch leads
• 8" x 11" posterboard
• fuse holder
• 1/4 amp fuse
• Hole puncher
• Two 22-gauge "bare" copper wires 24" long
• Twelve 9 inch wire strips
  
• masking tape and glue
• kitchen floor plan

Place the RISE girls into cooperative groups of four. Have the girls work together to share the responsibilities of recording data and manipulating materials.

1. Test each bulb by holding the wire ends to the terminals of the battery.

2. Print the kitchen floor plan and paste it to the 8" x 11" posterboard.

3. Next take the holepuncher and punch out the circles marked as hot and ground. These circles can also be identified by the drawn wire loops coming out from them.

4. Now, take one of the 22-gauged "bare" copper wires that is 24" long and start to wire the kitchen. To do this, you will create a loop that sticks out of the hole punched area on the kitcken floor map side, but allows for the rest of the wire to be on the bottom side of the poster board. You must use one wire for all the hot holes and the other wire for the ground holes.

3. Tape the wires to the bottom side of the kitchen floor poster board.

4. Have the girls draw a picture of the wiring done so far for the kitchen.

5. Connect the end of the wire that came from the hot holes to the fuse and then the fuse wire to the + side of the battery terminal. Now, connect the end of the wire that came from the ground holes to the - side of the battery terminal. Tell the girls that the wire from the hot holes would normally be red. Introduce the red to + rule.

6. Decide on the first "appliance"(Christmas light blub) to plug in and have the girls record it in their lab book. Wire a Christmas tree bulb to one of the loops from a hot hole and the other end of the Christmas tree bulb to one of the loops from the ground holes. If the bulb stays lit, then your "appliance" has not overloaded the circuit.

7. Repeat step 6 until the fuse blows (no light bulbs light up). Record the number of bulbs (appliances) it took to blow the fuse.

8. Now have the girls do some analysis of their kitchens. Teach the girls the following terms.

• Volts(V)
  A volt is a measurement that is used to measure the potential electrical energy.
• Amps/ampere(I)
  An amp/ampere is the measurement used to measure electrical current (the rate of flow of electrons in a circuit). 1 amp/ampere is equaled to 1 Coulomb of charge (carried by 6.24 billion-billion electrons) flowing past a point in one second.
• Coulomb
  A Coulomb is the charge carried by 6.24 billion-billion electrons.
• Ohm
  An Ohm is the unit for measuring electrical resistance (R).
• Ohm's Law
  States that the electrical potential difference (volts) is equal to the elecrical current (Amp) times the electrical resistance (Ohm). The formula for this law is V(volts)= I(amps) X R(Ohm)
• Watts
  The Watt measures the power of an electrical current. One Watt is the power made by a current of one amp under the pressure of one volt. (Electrical appliances are usually measured in Watts and their wattage is usually listed somewhere on the appliance.)
• Kilowatt Hour
  A Kilowatt Hour is the unit of measurement used by electrical companies to calculate their customer's bill. One kilowatt hour is equal to the amount of electricity needed to light ten 100 watt lights for a period of one hour.

   

9. The girls now need to find the current (amps) of the simulated kitchen. This is relatively simple to calculate because we have a clue. Look at the ampere on the 1/4 or 0.25 amp fuse. We can assume that the current of the kitchen was at least 0.25 amps. (You might want to use an ammeter to test the circuit to find out for sure.) Have the girls record this in their lab book.

10. Ask the girls "what type of circuit did they create?" The girls should identify the circuit as a parallel circuit.

Now tell them that they are going to calculate the current (amps) that flowed through each bulb. To do this, divide the current (0.25 amps) by the number of "appliances"(light bulbs) it took to blow the fuse.

For example: if only two light bulbs lit before the fuse blew, then the current passing through each light bulb would be calculated like this: 0.25 amps / 2 = 0.125 amps(I) per bulb. Have the girls record this in their lab book.

11. Have the girls now find the voltage (volts) in the circuit. This is really easy - have them look at the voltage of their batteries. (6 volt)

12. Now the girls are ready to calculate the resistance (Ohm) of each bulb. So far the girls have figured out the current that flows through each bulb (I) and the Voltage (V). Use the information collected so far to find the resistance (Ohm). Use this formula:

13. Lastly, the girls can figure out the wattage of each bulb by using the following formula:

14. Did the number of amps the circuit could support vary from the the number of amps of power or wattage? If the total of amps in the circuit was .25 and the number of the wattage coming from the circuit was .75, then your circuit overloaded and is a possible fire risk. Ask the girls if their kitchen has too many "appliances" in it and is a possible fire risk.

Each circuit in a normal home can usually support around 20 amps of power. This means that the appliances plugged into any circuit should never exceed a total of 20 amps.

If you go over this total your could "overload" your circuit. When a circuit is "overloaded" it becomes dangerously hot. If this happens, a fuse on the circuit will melt to "break" the circuit and prevent an electrical fire. Modern circuit fuses simply"trip or throw" a switch to its off position when a circuit gets over-loaded. Once the source of the "over-loading" is removed, the circuit can be reset by placing the fuse switch to the on position.

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