talking about how electricity is transferred from the power plant to the home.
it comes out from the plant at like 12000V, then using transformer is pumped up to like 240000V (keeping in mind that it's AC, which is why it can be transformed) this high voltage is necessary coz if resistance remains the same but voltage is increased, current decreases, and when current decreases, heat decreases (heat is produced when a current flows through something)
the electricity is carried on large structure thingos, high off the ground to prevent people getting shocked and stuff (electricity can jump at such high voltages)
the electricity is transformed down to 8000 in closer, more local areas, and transformed again near homes so that it gets down to 240V, which could still be fatal, but there isn't as much risk of the electricity jumping.
the electricity can't go through the pole because the pole would heat up and people who touch them could get electricuted. so, the electricity is diverted; isolated away from the pole, they are detoured around with other cables, and ceramic discs are used to prevent the electricity from getting to the posts (ceramics cant hold water and cant conduct electricity anyway) the higher the voltage, the more ceramic discs basically.
some power.. tower thingies.. what are they called? dont detour around poles, instead the electricity runs through the same cable, but are connected to the.. big crap but isolated using the same discs, but heaps more of them.
there is also usaully cables all the way up the top, in case of lightning. the lightning would go into those cables, and since they're touching the structures, would go all the way down to the ground and get earthed.
Showing posts with label motors and generators. Show all posts
Showing posts with label motors and generators. Show all posts
Thursday, May 13, 2010
Thursday, April 22, 2010
phys (0422) - M&G: induction
a man named orsted figured that moving a current next to a compass had an effect on it.
another dude called faraday took this idea that magnetism and electricity were related and experimented with it. he moved a magnet towards and near a coil and realized that it produced a current (shown by a galvanometer)
thing is, current is only induced if there's a change of flux (that is, magnetic field strength) so using a simple DC power supply would not be the same as AC. alternatively, stationary magnets wont do anything, it has to be like, moving.
a generator looks like a motor but is basiclaly the opposite.
i'm realy tired and lazy so i'll edit this later.
another dude called faraday took this idea that magnetism and electricity were related and experimented with it. he moved a magnet towards and near a coil and realized that it produced a current (shown by a galvanometer)
thing is, current is only induced if there's a change of flux (that is, magnetic field strength) so using a simple DC power supply would not be the same as AC. alternatively, stationary magnets wont do anything, it has to be like, moving.
a generator looks like a motor but is basiclaly the opposite.
i'm realy tired and lazy so i'll edit this later.
Thursday, March 11, 2010
phys (0311) - M&G: [p] dc motor
today we had to make our very own makeshift dc motor completely on our own.
i cbf getting into deets of how we failed, but the final result was that we had one working for at least a minute.
we used a copper wire twisted into turns for our coil, suspended by paperclips over a.. neo.. something magnet.
the paper clips and magnet were taped down to the table, and the paper clips were gonnected to the transformer using alligator clips.
so it worked, kudos to the workings of the motor effect.
im falling asleep.. cya guys
i cbf getting into deets of how we failed, but the final result was that we had one working for at least a minute.
we used a copper wire twisted into turns for our coil, suspended by paperclips over a.. neo.. something magnet.
the paper clips and magnet were taped down to the table, and the paper clips were gonnected to the transformer using alligator clips.
so it worked, kudos to the workings of the motor effect.
im falling asleep.. cya guys
Tuesday, March 9, 2010
phys (0308) - M&G: parallel wires
something i acutally learned in the other class.. the force between two parallel wires carrying currents:
F I1 I2
_ = k_______
l d
where:
F = force
l = common length of wires
k = constant: 2x10^-7
I = current of the two wires respectively
d = distance betwen wires
opposites repel when it comes to currents.
first of all, use right hand grip rule to work out the field around the wires, and from there, use right hand palm to see force.
can observe thattt..
two wires with current in the same direction would experience force that would make them come closer together..
likewise
two wires with current in opposite direction would experience a force that would make them get further away.
...yay
F I1 I2
_ = k_______
l d
where:
F = force
l = common length of wires
k = constant: 2x10^-7
I = current of the two wires respectively
d = distance betwen wires
opposites repel when it comes to currents.
first of all, use right hand grip rule to work out the field around the wires, and from there, use right hand palm to see force.
can observe thattt..
two wires with current in the same direction would experience force that would make them come closer together..
likewise
two wires with current in opposite direction would experience a force that would make them get further away.
...yay
Thursday, March 4, 2010
phys (0304) - M&G: [p] the motor effect
we were meant to plan the investigation ourselves today.. and our method actually came from david. thanks to him, we were able to complete the task really quickly and get straight to the written work.
basically.. we connected a conducting string to a transformer using wires. we put the string over a magnet (north pole) and turned the transformer on (DC). we observed that the string went one way. this wouldve been the result of a force.
after this, we turned the magnet around so that the south pole was under the string, and after turning the transformer on, the string went the other way.
using the right-hand palm rule, we proved the reason the force pushed the conductor one way or ther other, since it carried a current in a magnetic field.
haev a look at what was written in book.
basically.. we connected a conducting string to a transformer using wires. we put the string over a magnet (north pole) and turned the transformer on (DC). we observed that the string went one way. this wouldve been the result of a force.
after this, we turned the magnet around so that the south pole was under the string, and after turning the transformer on, the string went the other way.
using the right-hand palm rule, we proved the reason the force pushed the conductor one way or ther other, since it carried a current in a magnetic field.
haev a look at what was written in book.
Tuesday, March 2, 2010
phys (0302) - M&G: force between parallel wires
cheat lesson, second physics period for the day since no teacher showed up for biology.
they were talkinga bout something we havent yet done in our class.. doing things different order i guess.
the force between two parallel wires, uses the right hand grip rule to show which way the magnetic field is going.
now on a single wire that doesnt matter.. but with two parallel wires, it does. alternating currents will result in a strong force in a single direction, whereas two currents in the same direction would result in forces going perpendicular to the wires (up and down)
the formula goes like this..
F I1 I2
_ = k_____
l d
where:
F = force in N
l = length of wires in m
I1 and I2 = current of two wires
d = distance between wires in m
k = 2 x 10^-7 (i forget the word mr robson used, it's to do with how well magnetic fields act in different mediums, in this case its for air and vacuum)
they were talkinga bout something we havent yet done in our class.. doing things different order i guess.
the force between two parallel wires, uses the right hand grip rule to show which way the magnetic field is going.
now on a single wire that doesnt matter.. but with two parallel wires, it does. alternating currents will result in a strong force in a single direction, whereas two currents in the same direction would result in forces going perpendicular to the wires (up and down)
the formula goes like this..
F I1 I2
_ = k_____
l d
where:
F = force in N
l = length of wires in m
I1 and I2 = current of two wires
d = distance between wires in m
k = 2 x 10^-7 (i forget the word mr robson used, it's to do with how well magnetic fields act in different mediums, in this case its for air and vacuum)
phys (0302) - M&G: motor applications
besides discussing the answers to yesterday's question set, mainly talked about two cases here..
a loudspeaker uses an AC motor.. alternating current meng.
it goes like this.. the speaker slots into a round magnet, with north in the middle, and south around it. when a current is put through and around the thing, it pushes the speaker out.. and when the current switches (AC) it comes back.. the vibration causes sound.
to increase volume (aplitude) the current would be turned up.
to increase pitch (frequency) the frequency would be turned up.
the other case sues a DC motor, a galvanometer (or ammeter)
its got the same structure as a regular DC motor, but there is a spring with produces tension, which prevents the arm from continuously spinning. the more current that is put through, the higher the force, and thus the further the needle points.
a loudspeaker uses an AC motor.. alternating current meng.
it goes like this.. the speaker slots into a round magnet, with north in the middle, and south around it. when a current is put through and around the thing, it pushes the speaker out.. and when the current switches (AC) it comes back.. the vibration causes sound.
to increase volume (aplitude) the current would be turned up.
to increase pitch (frequency) the frequency would be turned up.
the other case sues a DC motor, a galvanometer (or ammeter)
its got the same structure as a regular DC motor, but there is a spring with produces tension, which prevents the arm from continuously spinning. the more current that is put through, the higher the force, and thus the further the needle points.
Monday, March 1, 2010
phys (0301) - M&G: DC motor
split ring commutator.
an important term, remember it. it's the part of a DC motor that changes the direction of the current. other important parts include:
power source (battery)
brushes (made of carbon)
magnet
coil
having concave magnets also is better than having just plain straight magnets because there's a wider spread of magnetic field, thus a smoother turning motor.
we did learn a new formula today, it goes:
T = nBIAcos@
where:
T = torque
n = number of turns (loops of the wire in the coil basically)
B = strength of magnetic field in teslas (T)
A = area in m^2
cos@ = angle between plane of coil and the magnetic field. it becomes cos now since it is equal to 1 when the coil is perpendicular to the field
double check whether its perpendicular or parallel..
an important term, remember it. it's the part of a DC motor that changes the direction of the current. other important parts include:
power source (battery)
brushes (made of carbon)
magnet
coil
having concave magnets also is better than having just plain straight magnets because there's a wider spread of magnetic field, thus a smoother turning motor.
we did learn a new formula today, it goes:
T = nBIAcos@
where:
T = torque
n = number of turns (loops of the wire in the coil basically)
B = strength of magnetic field in teslas (T)
A = area in m^2
cos@ = angle between plane of coil and the magnetic field. it becomes cos now since it is equal to 1 when the coil is perpendicular to the field
double check whether its perpendicular or parallel..
Sunday, February 28, 2010
phys (0225) - M&G: torque
torque (measured in Nm) is a rotational.. force? calculated using the formula:
T = Fd
where T = torque in Nm
F = force in N
d = distance in m
in particular situations where applying maximum force still doesnt cause any torque (rotation) the distance (radius) has to be increased eg. lengthening a spanner to twist bolts
in a motor.. this torque is produced in a coiled current-carrying conductor, because of the motor effect. however, if the current was going in the same direction in the wire, by the time it rotates 180*, the current would be going the other way in relation to the magnetic field, so it would turn the other way. in order for the coil to keep rotating, the current must be pushed in the other direction.
T = Fd
where T = torque in Nm
F = force in N
d = distance in m
in particular situations where applying maximum force still doesnt cause any torque (rotation) the distance (radius) has to be increased eg. lengthening a spanner to twist bolts
in a motor.. this torque is produced in a coiled current-carrying conductor, because of the motor effect. however, if the current was going in the same direction in the wire, by the time it rotates 180*, the current would be going the other way in relation to the magnetic field, so it would turn the other way. in order for the coil to keep rotating, the current must be pushed in the other direction.
phys (0224) - M&G: F = BIlsin@
we went over a formula that calculates the force experienced by a charge running throuhg a magnetic field.
F = BIlsin@
where F = force in newtons (N)
B = strength of magnetic field in teslas (T)
I = current in amperes (A)
l = length of wire in metres (m)
sin@ = sine of theta.. which is @.. the angle of the wire against the field
F = BIlsin@
where F = force in newtons (N)
B = strength of magnetic field in teslas (T)
I = current in amperes (A)
l = length of wire in metres (m)
sin@ = sine of theta.. which is @.. the angle of the wire against the field
phys (0222) - M&G: magnetic fields
MOTORS AND GENERATORS
hurrah new topic, and just when iw as getting used to space and special relativity and whatnot.
so. motors and generators.
the motor effect is a force experienced by a current-carrying conductor in a magnetic field.
the right-hand palm rule is important. ie. our fingers represent a magnetic field, our thumb represents a perpendicular current, and the "force" comes out of our palm.
magnetic fields are produced from and around magnets and electrical currents, and things like solenoids.
a magnetic field is a region.. something something about forces. LAWL i better check up on that. but yeah.
fields travel from north to south on a magnet always, and what makes solenoids different is they have a field within them as well.
hurrah new topic, and just when iw as getting used to space and special relativity and whatnot.
so. motors and generators.
the motor effect is a force experienced by a current-carrying conductor in a magnetic field.
the right-hand palm rule is important. ie. our fingers represent a magnetic field, our thumb represents a perpendicular current, and the "force" comes out of our palm.
magnetic fields are produced from and around magnets and electrical currents, and things like solenoids.
a magnetic field is a region.. something something about forces. LAWL i better check up on that. but yeah.
fields travel from north to south on a magnet always, and what makes solenoids different is they have a field within them as well.
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