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Tuesday, 8 January 2008
Electric power and Circuits Blog

Answer the questions below.

1.  Which draws more current, a 100 W bulb or a 75 W bulb?  Which has a higher resistance?


2.  Why is it dangerous to replace a 15 A fuse that blows repeatedly with a 25 A fuse. 


3. Discuss the advantages and disadvantages to connecting Christmas tree lights in a series circuit, and a parallel circuit. 

Posted by georgecelona at 3:15 PM EST
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Tuesday, 8 January 2008 - 9:23 PM EST

Name: "Matt Hazzard"

1.  Since both are are a series circuit they both will use the same amount of voltage in the system.  But since the 100W bulb has more power, and P=IV, it will need more current to run the 100W bulb than the 75 W bulb.

2.  The reason that the 15 A fuse is blowing repeatedly is that you are demanding too much current from the circuit already.  By increasing the fuse to a 25 A fuse you'll only demand more current which the circuit can't handle already.

Tuesday, 8 January 2008 - 9:26 PM EST

Name: "MaryBeth"

A 100 W bulb will draw more current because I is P/V therefore, the higher the power, the higher the current. A 75 W bulb will create more resistance because R is V^2/P (with substitution), therefore smaller power sources will create more resistance just as 1/2 is greater than 1/3.

 Replacing a 15 A fuse that continues to short out with a 25 A fuse is extremely dangerous because circuit breakers trip a circuit when they become overloaded with too many devices. If you put a larger fuse on, the circuit won't short out when the wires are overloaded, creating too much thermal energy which may potentially start a fire.

Christmas tree lights are better in parallel because if one bulb goes out the rest can continue to burn. Also, such a set-up results in brighter lights overall. If the string of lights was a circuit in series, one bulb being removed could make the whole chain go out which is just no good. You'd like...ruin Christmas. 

Tuesday, 8 January 2008 - 9:39 PM EST

Name: "Dave"

1)   the 100 W bulb draws more current because P = IV, therefore P/V = I, so Current is directly proportional with power.  However, the 75 W bulb would have more resistance because R = V^2/P, so power is inversely proportional to Resistance.

2)  If the 15A fuse blows, it means that too much current is passing through the circuit for the wiring to handle without overheating.  With a 25 amp fuse, the wiring would be able to overheat because the fuse would blow at a higher current, thereby causing a major fire hazard.

3) with a series circuit the christmas tree lights would have an equal current all the way through, so the fuse can't blow, but have more resistance so they may be dimmer.  A parallel circuit would have less resistance, meaning brighter light given off, however, current would be the sum of currents from all of the junctions, meaning a higher current, which could short out the lights

Tuesday, 8 January 2008 - 9:44 PM EST

Name: "Dylan Knaggs"

1. Because I=P/V, the bulb with the higher power (100W) would also have a higher current. However, because P=V^2/R, the 100W bulb would have a lower resistance.

2. A fuse with 25A should not be used (or a fuse with any higher A) because the 15A fuses' blows are a result of overloads that cause the circuit to open.  This blow is a good thing because it prevents overheating that can cause a fire. Using a 25A fuse may not allow this fuse to blow, and the overheating could occur.

3. In a parallel circuit, one light could go out and all the others would be unaffected. In a series circuit, one bulb going out would prevent current going to the others. Parallel circuits also would cause the lights to be brighter because resistance would be lower, so both current and power would be higher. An advantage of series circuits is that the brightness would be even throughout the bulbs because current is constant in a series circuit, andthis means that power would be as well.

Tuesday, 8 January 2008 - 9:55 PM EST

Name: "D. Wilson"

As both Matt and MaryBeth explained, the 100 W bulb will require more current to run since P=IV.  Also, since power is inversely proportional to resistance, the smaller the wattage, the greater the resistance, so the 75 W bulb will have greater resistance.

Replacing the 15 A fuse with a 25 A fuse would be extremely dangerous as it would create a potential fire hazard.  The fuse is blowing because it can't handle the current that is passing through it.  If you replaced it, the fuse wouldn't blow out, it would overheat and could start a fire.

Christmas tree lights are better in a parallel circuit because one light going out would not affect the entire string of lights.  If they were in a series circuit and one light went out, the entire string would go out as well.  The lights would also be brighter all the way through in a parallel circuit then a series circuit. 

Tuesday, 8 January 2008 - 10:24 PM EST

Name: "Meghan"

Out of the 100 W bulb and the 75 W bulb, the 100 W bulb would have more current since P = IV.  However, the 75 W bulb would have more resistance since P = V^2/R.

 It is dangerous to replace the 15 A fuse with a 25 A fuse because the new fuse would only require more current, and more power would also be needed.  If the circuit can't already handle the power of a 15 A fuse, it will definately not handle a 25 A one.

 It would be better to use a parallel ciruit for Christmas lights because they would all get the same voltage, so they would shine brighter than those in a series circuit.  It is also better because if a light goes out, which they usually do, not all of the other lights would go out since the lights aren't really dependant on eachother like they would be in a series circuit.


Tuesday, 8 January 2008 - 10:27 PM EST

Name: "Matthew Correnti"

1.  The 100 W light bulb draws more current and the 75 W light bulb has a higher resistance. 

2.  It is unwise to replace the 15 A circut breaker with a 25 A circut breaker because the 15 A is there for a reason.  It is likely that the electronics connected to the system will be damaged with a current higher than 15 A, so allowing more current to flow through the circut would be detrimental to the equipment.

3.  Christmas tree lights in a parallel circut would have the advantage of being brighter and being able to withstand a burned out bulb or two.  However, if the resistance of strands differs, the current running through each will vary, causing the brightness of the bulbs to be inconsistent.  A series circut would ensure an even brightness but be a disadvantage because one burned out bulb could ruin your christmas celebration.

Tuesday, 8 January 2008 - 11:21 PM EST

Name: "Kevin Crowe"

1. The bulb that draws more current is the 100 W bulb, and the 75 W bulb has the higher resistence.


2. It is dangerous to replace a 15 A fuse with a 25 A fuse because the 15 A fuse was meant for only 15 A and if you replace it with a 25 A fuse then the circuit system will be damaged. The system was most likely meant for a 15 A fuse if thats what is being used. It would not be wise to allow more current to flow in because the system would not be able to handle it, much like Correnti cannot handle me in ping pong.


3. As Matt said, If you connect christmas tree lights in a series of circuits then the lights would appear brighter. Also if there was burned out bulb it wouldn't effect the other lights, unless the resistance is different throughout the series of circuits then that could effect the brightness.

Tuesday, 8 January 2008 - 11:23 PM EST

Name: "anonymous"

1.) The 100 W bulb would draw more current since power is directly proportional to current. However, the 75 W bulb would have more resistance since power is inversly proportional to resistance.

2.) Replacing a 15 A fuse with a 25 A fuse is very dangerous. Because if the the circuit is created for a 15 A fuse then it should not be replaced by a higher one. There are a few reasons taht may cause a fuse from blowing, but the reason it is blowing is to prevent overloaded wires from getting hot enough to start a fire. However, if you replace it with a higher fuse then the scenario is likily to happen.

3.) The parallel circuit have a few advantages. They will have brighter lights because of lower resistance and if one light goes out all the toher lights wouldnt go out like they do in a series circuit. However, if the resistance of a parallel circuit is not equal throughout it could cause the brightness to be inconsistant. In saying, this the advantage to a series circuit be that they would have an even brightness throughout.

Tuesday, 8 January 2008 - 11:24 PM EST

Name: "J. Mahon"

Joe Mahon is anonymous

Tuesday, 8 January 2008 - 11:58 PM EST

Name: "Chris Addis"

1. The one that will have the larger current is the hundred-watt bulb because when you look at the equation I = P/V. The hundred watt bulb will require more power then the seventy-five watt bulb and both light bulbs will be receiving the same voltage so, that means that the current would have to be larger on the hundred watt bulb. The one that will have the larger resistance will be the seventy-five watt bulb because when you look at the resistance equation it  is V2/P.  This means the one with the lower power or the seventy-five watt bulb would have the greater resistance.

2. The reason why replacing a fifteen A fuse with a twenty-five A fuse is dangerous is simple. A fuse is meant to prevent the device from overheating and causing any damage to the device or the surroundings. By increasing to a twenty five A fuse your chances of it burning out are less likely but, there is a huge downside your risk of overheating is increased by a considerable margin. The reason that the fifteen A fuse is blown repeatedly is because you are running too much power through that device and it is breaking as a safety precaution to prevent the wires from heating up to much which could lead to a fire or an electric discharge. It is a lot safer and smarter just to keep replacing the fifteen A fuse then to take the added risks of the twenty five A fuse.

3.  There are both advantages and disadvantages to having Christmas tree light that are in a series circuit or ones that run in a parallel circuit. If it is in a series circuit then the lights will be at the same level of brightness throughout due to the fact that each light will have the same current. However if one of the bulbs were to burn out or just die then the rest of the lights would go out since the electricity no longer has the full path to travel. If it is in a parallel circuit then the lights would get brighter as the chain when on since after each bulb the next one would have less resistance. Another advantage is that some of the lights could burn out and then rest will still function since it is a parallel circuit. A disadvantage is that since the resistance is lower as the chain goes on this means that the current and the power would increase which could limit how long you could make it since if it were too long then the bulbs would just burn out.

Wednesday, 9 January 2008 - 9:42 PM EST

Name: "Jonathan Hellmer"

1.  The 100w light bulb will draw more current since the power is directly proportional to the current.  But, the 75w will light bulb has a higher resistance because power is inversely proportional to resistance.

2. It is dangerous to replace a 15 A fuse that blows repeatedly with a 25 A fuse because the 15 A is the fuse suited for that certain utility.  Therefore, if there is a fuse higher than 15 A placed in that slot there could be damage done because this means that there will be more current running through that system than if the system is not able to handle that high of a current it can be dangerous by affecting that utility.

3. The advantages and disadvantages to connecting Christmas tree lights in a series circuit, and a parallel circuit are, that in a parallel circuit the Christmas lights would be brighter and they would also be able to stay lit even if a couple of light bulbs were to burn out.  But, then there is the case that if the resistance in the different strands is different the current that will run through each strand will be different so the brightness of the bulbs could end up being inconsistent.  If you have a series circuit connecting your Christmas lights you will be sure to have an even brightness throughout the entire circuit but the disadvantage to this type of circuit is that if one light bulb were to go out it would disrupt the flow of the current and all of the light bulbs would go out.

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