 If it doesn't work for you, don't worry about selecting your seat. And if you can't select your seat properly and the grouping tool doesn't work for you, I give you permission to please join other groups as necessary. And if you're a person, the Picker Tool does work for you and it's telling you who to talk to, please let other people in on your discussions to other people that might not have been included in that. So please be collaborative and discuss everyone together. Okay, so today we're going to talk about the electric field. But before we get there, we've got a couple more problems about charges and forces. So your first catalytic question is here. Please take a look at this, think about it by yourself and click in with your answer. We're going to do a revoke on this one. So your device should tell you who to talk to. Please hear that person, tell them what you got and why, and then click in once you come to the consensus. I saw here, when I saw here, it's a shift to the answer B. So we've got a majority on B now. How come? So as these charges are moving further away from each other up here, the horizontal vectors are kind of canceling out so there's less force. And that's exactly what's going on here. So slightly spread out to the side. The net force from those will be weaker because they're not pushing directly up. So an alternate way to think about this, we can draw the vectors also. So if we have a vector, we can draw the vector from the 3Q charge at the top. It might be a vector pointing straight down like this. That's the direction of the force. Or it's the ones from the bottom. You get a vector straight up from the charge in the middle. And then you get a vector in this direction from the charge on the right, one in this direction from the charge on the left. So when you add those three vectors together, the net force in the out direction is going to be less than the force coming from the charge 3Q at the top. So C is the answer here. Are there any questions about these two problems? So Michael Farage is a really interesting character in the history of physics. So he actually didn't go to school for very long. I believe he was kicked out of school when the teachers thought he was down or something like that. So he didn't go to school for very long at all. He worked as a bookbinder's assistant. So during the day he'd buy books. And at night he'd read books and he became very inspired by science. So eventually he got a grade as an assistant to a scientist. And from there he started being able to do experiments with electricity and magnetism. And so he came up with this concept of the electric and magnetic fields. Now people didn't really take it seriously because he didn't have the mathematical background to be able to really nail down what these fields were. So it wasn't until 20 or 30 years later when Maxwell came along and figured out the mathematics that people took it seriously. But Faraday was a scientist and he was almost on the level of Newton and Einstein in terms of the discoveries they made. So this is one picture of Faraday. He looked pretty distinguished there. Here's another picture of him. So this is him. This is an animation picture that I took from Cosmos, Neil deGrasse Tyson Cosmos down here. So I just want to put in a little plug for that. I'm interested in science stories and things like that, which I really enjoyed this episode. You can learn a little bit more about Michael Faraday there. So that's on Netflix, if you have Netflix, any interest. How do you know there's an electric field in space somewhere? Well, you can tell if there's an electric field by the force that it exerts on a charge. Well, there's no electric field in this room. You bring a charge into this room and measure if there's a force on it. Your next question here gives you a little bit of practice with this definition of the electric field. So please take a moment to read that and answer it. In case it's not clear, this charge here is three corals. This one is two corals. And this is the one coral charge. We've got a majority. We've got a majority on two mutants, which is the correct answer here. I'll give you guys practice with this unit vector thing. So on your worksheet here, we've got a question. I want you to draw the regular unit vector, this vector on our half, around negative charge. So please go to your worksheet now. Draw what you've got on there. We'll look at it in a moment. It's a bit of a mess. A bit of a mess. Would anybody like to, you know, maybe tell me what would they actually do? And why? So it looks like there's a lot of arrows going out or in or something. Can anyone be a little more precise all of it? So back there. What you need to do your vector is pointing away because the unit radio vector always points away. And you feel it can be different from the unit vector. Do we have a green? Or anybody who disagrees with that? Did anybody get something that looks like this? See some hands. Why like this? What's your name? Be like this because when you're looking at a charge, you use a proton or a positive charge as a test part. Powering on, let's talk about some electric fields. So I've got your next catalytic question here. Please take a look at it. Answer it by yourself. Another good majority here is on, is for D. And so again, this is just practice adding up vectors together and trying to see what will result from that. So awesome. So we've got some practice doing this vector addition sort of qualitatively and trying to figure out what we expect the electric field to do. So in your next problem, we're going to get a little more quantitative about it. So before I let you go and work on this, I want to get some intuition for what this should be. So can someone tell me what direction the electric field at point A is due to charge 3 this 5-nanofilum charge will be. What direction will that electric field be? So next up, we'll need to calculate the vector electric field due to the other point charges 2 and 3. We're not going to have time to do that in class today. So I'm going to ask you to finish that for homework. I'm going to post the solution online in the slides within the next hour or so to go on there and check. But this is a very good practice question, especially for your quiz coming up on Wednesday. So please make sure it's nice and timely.