 Quiz number one stream of protons is acted upon by a magnetic force of Blah blah blah blah blah while traveling now here's the key they have to be perpendicular if they're parallel There is no force That's my way of saying probably somewhere on the multiple choice of your test still I'm gonna give you at least one in the picture where they're parallel And I'm gonna tempt you to think there's a force but the answer is no force or it's gonna go in a straight line It's not gonna curve at all but you know What speed are the protons traveling at so we said this the force quite please the force The magnetic force on a charge is QVB. I'll give you a half mark for writing that I Think that means that the speed is equal to the force divided by QB the speed is equal to 4.8 times 10 to the negative 14 Divided by oh, they didn't give me the charge Did they need to give me the charge? Justin I say to you no no because it's a proton and that's on my sheet. It's the elementary charge of 1.6 times 10 to the negative 19 coulombs and The magnetic field is pretty big 0.5 Tesla's 4.8 10 to the negative 14 divided by Bracket 1.6 negative 19 times 0.5 The answer is 600,000 or 6.0 times 10 to the fifth meters per second now technically if you wrote 600,000 that's one thing fake I'm not gonna freak but they might for those of you that are writing on the provincial You know what I notice I have one two three four lines two marks How about half mark for each one of those, but if you got the right answer for once number two a wire carrying a current of Four amps is shown in the above diagram If the force that the wire experiences is 1.4 times 10 to negative 2 Newtons What's the strength of the magnetic field so the magnetic field? Magnetic force in a wire Is built and they want me to find the strength of the magnetic field they want me to find B Which is going to be f divided by B. L. It's going to be 1.4 times 10 to the negative 2 divided by Be I did I say be yeah, thank you divided by I I L. Thank you. Something was bugging me. I hadn't quite figured it out yet because it's going to be four amps now look up This is too easy. It actually is for physics 12 and so Sally what they will always do to make it a tiny bit more difficult They'll give you the diagram and they will always give you the total length of the wire and the length of the magnetic field They will always give you two lengths Which length do you think I'm going to use? Well, which section of wire is undergoing the force all of it? No, just the section that's in the magnetic field I'm going to use the point zero four two and they'll do that if you do the review if you work on the review You'll notice in almost every diagram. There's always two lengths Also, especially because it's multiple choice It lets them make up more wrong answers that you might get Point zero one four that is one point four times ten to negative two divided by bracket four times point zero four two point zero eight three three so zero eight three three Teslas are eight point three times ten to negative two Teslas Seems reasonable. What's a big magnetic field in Teslas? Like fifty or a hundred if you get an answer of two thousand Teslas, I doubt it And maybe at the large Hadron collider they're getting stuff like that, but I doubt it, right? What's the direction of the magnetic fall? Okay? Oh Thumb in the direction of the current which for me is to my left. That's to your right fingers into the page down the page Hopefully you figured out that there was a Part two on the back. Sorry. I couldn't fit it all one page an electron traveling at five times ten to the sixth Mutant for second moves perpendicular. Okay, that's good to a magnetic field. Oh What's the magnetic what's the magic of the force the force is Just Q V B It's equal to Q electron 1.6 times 10 to the negative 19 V five times 10 to the sixth B eight point five times 10 to the negative three 1.6 times 10 to negative 19 times Five times 10 to the sixth times 8.5 Times 10 to the negative three six point eight times 10 to negative 15. Is that right? Yeah Six point eight times 10 to the negative 15 Newtons B Electron is forced into a circle. Oh Magnetic force equals circular force Q V B equals M V squared over R Yay one V cancels. What do they want me to find here? radius is M V over Q B now I'm going to pause for a second this Situation is the most common using principles of physics right to explain Question that they'll ask so they'll say something like this. I'll ask you to find the radius and then part B They'll say what if you had twice the charge? What would the radius be? Bigger smaller or the same Twice the charge would give you an extra two down there. I think Justin would make the radius smaller. Oh What if instead of an electron it was a proton? What would the radius be bigger smaller? Or the same Proton would have the same charge. Oh, but a bigger mass bigger radius What if it's same electron, but we were traveling faster Bigger radius if we were using a voltage to accelerate the electron like an electron gun like a cathode ray tube What if we drop the voltage? You drop the voltage it will be traveling slower Smaller radius. So there's all sorts of different ways starting from here And you'll see a bunch of them on the right hand rule sheet that is due as well as an assignment that I emailed you an answer key for the other day and You'll see a bunch of them on the great big review that I have a handwritten answer key for online. Okay Meanwhile here 9.11 times 10 to the negative 31. I think that's a massive electron How fast? 5 times 10 to the 6th Negative 6 no 6 mr. Duke all over 1.6 times 10 to negative 19 and 8.5 times 10 to the negative 3 What'd you get? What's the radius? 3.35 times 10 to negative 3 is that right people on it 3.35 times 10 to negative 3 meters See what's the kinetic energy of the electron? Hey kinetic energy hasn't changed since grade 11. How do I calculate kinetic energy? half mv squared Potential energy has changed We've got like four different ways because it depends now Justin on what type of potential energy Gravitational on earth gravitational cosmic electric potential We did one more. I think but I can't remember. Anyway, we got several different options, but kinetic same old same old It's gonna be a half mv Square What'd you get friend? What'd you get doing? Oh See I'm kind of sense. I'm starting out. Sorry Didn't have a calculator. You didn't need one for that. Come on. It's half of that. It's a ninth. Oh, come on Adding some exponents, please What'd you get 1.14 times 10 to negative 17 1.14 Times 10 to negative 17 units Ryan Thank you. We're doing the homework. Is that right? Yeah. Yes. Okay last one What's the magnetic field strength inside of so one? Okay, so magnetic field of a solenoid is Mu naught and it's either n i Over l or it's little n times i depending whether they gave me the total number of coils and the length or The number of coils per meter I think here they gave me the total number of coils. So mu naught the permeability of Free free space space bit my favorite constant four pi Times 10 to the negative seven n is six hundred i is two point five l is not four What is l? 0.04 they don't very often make four meter long solenoids I'm sure there are some applications, but not common household everyday ones What'd you get point zero four seven Tesla's is that correct? No, yes. Yep people nodding two marks. I probably go One mark for that half mark for the numbers half mark for the answer four seven or four six four seven No, people are not people are frowning. Okay, let's try this better double-check this one four Hi scientific notation, but negative seven times six hundred times two point five divided by point zero four Yeah point zero four seven sorry Tesla's give yourself a score out of 13 and pass them in