Millikan Oil Drop Experiment - Video Tutorials & Practice Problems
Get help from an AI Tutor
Ask a question to get started.
The Oil Drop Experiment helped with determining the fundamental charge of the electron.
The Oil Drop Experiment
1
concept
Millikan Oil Drop Experiment
Video duration:
4m
Play a video:
Hey everyone. So here we're going to say that in 18/97, JJ Thompson's Cathal Ray 2 experiments led to the discovery of the negative charge of electrons. But what we can say further is that Thomson was unable to determine how much negative charge an electron possesses and it wasn't until at 1913 where Robert Milliken and Harvey Fletcher discovered the fundamental charge of an electron. Now here we're going to talk about the Milliken oil drop experiment. Here we're going to say that Milliken and Fletcher used oil droplets, charged plates, gravity, and x rays to determine the amount of charge. And here there are certain things that we need to remember. We have our atomizer. This is just the container used to disperse the individual oil droplets. Here in this drawing, we can say that this is our atomizer. And what we do here is we would basically drive this atomizer into this opening and basically squeeze on the nozzle and a mist of oil droplets will be sprayed within our apparatus. Next, we need to realize that we have something called electric force. This is basically the attractive and repulsive forces between particles based on electric charges. Remember in chemistry, opposite charges attract. We're gonna say same charges repel. Now, once we've stuck in this atomizer and basically dispersed our oil droplets into the apparatus, here we have our oil droplets, these little dots. What happens here is these oil droplets are going to fall through here, this plate. This plate here on top is our positively charged plate. Okay. Now, going back to the experiment, the oil droplets we say were introduced to the atomizer. They go through the positive plate. Here, this is our x-ray source, so it's basically going to zap our oil droplets. So, the x-ray source zaps our oil droplets to give them a negative charge. Here we have our microscope which basically looks at our charged oil droplet which would be this little dot right here. So here that's our charged oil droplet. And this blue plate here would just be our negatively charged plate. Now this box here would be our voltmeter which will read the, the voltage or charge that could be produced within this experiment. Now, here if we turn on the power of the charged plates, it's going to create an electric field. And, what's important about this electric field is we're going to say that if the voltage is turned up and it becomes greater than the force of gravity, then the droplet itself will rise. But, if the voltage is not high enough and it's less than the force of gravity then the oil droplet will fall. What we have to do here is we have to apply the right amount of voltage that'll help, if we can do it, help the droplet be suspended in air And if we could suspend that droplet in air between our positive and negative plates, it's through the suspension that we can figure out the charge of our electron, and that's what they were able to do with this experiment. See, through the suspension of the oil droplets, the charge of an electron was determined to be negative 1.60 times 10 to the negative 19 coulombs. Coulombs representing charge. Okay. So just realize that when it came to the Milliken oil drop experiment, it helped to further the experiment of Thompson. It helped us to figure out the amount of negative charge on any given electron.
2
example
Millikan Oil Drop Experiment Example 1
Video duration:
2m
Play a video:
We're told that the fundamental charge of an electron is negative 1.60 times 10 to the negative 19 coulombs. If a scientist determines the charge to mass ratio of an electron is negative 1.76 times 10 to the 8 coulombs per gram, what will be the total mass of an electron? Alright. So for a question like this, they want us to determine the the total mass. So that is what our end amount needs to be. So end amount here will be the grams of our electrons. And our given amount, remember, our given amount is when we have a value that has only 1 unit connected to it. And here, that 1 unit could 1 unit by itself would be this charge of an electron. So that's our given amount, 1.60 times 10 to the negative 19 coulombs. Remember, don't forget the negative sign. Now to go from the given amount to the end amount, we have to utilize conversion factors. Remember, conversion factor is when you have 2 units tied together. Our conversion factor here would be negative one point 7 6 times 10 to the 8 coulombs per gram. Coulombs and grams are 2 different units that are being tied together. We need to cancel out coulombs, so we put the negative 1.76 times 10 to the 8th coulombs on the bottom, and that's for every 1 gram. So this would represent our conversion factor. And we'd see here that coulombs would cancel out and I have as my units at the end, grams, which is what I'm looking for. So all we have to say here is this question requires only one conversion factor. So then it's just going to be this value here divided by this value here and that'll give us our grams. Remember when you have a number written in scientific notation you need to put it in parenthesis. Otherwise, you may get the incorrect answer. If you do this correctly, you'll get approximately 9.10x10-twenty 8 grams as the total mass of your electron. So based on that answer, option would be the correct choice.
Do you want more practice?
We have more practice problems on Millikan Oil Drop Experiment