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# Old Fleming's Left Hand rule watch

1. Hey!
I understand the directions of each finger, but i'm confused about which way your finger points for the direction of current flow, now usually current flows from negative to positive, but i swear in this rule you have to do from positive to negative? Can somebody please help?
Thanks
Hey!
I understand the directions of each finger, but i'm confused about which way your finger points for the direction of current flow, now usually current flows from negative to positive, but i swear in this rule you have to do from positive to negative? Can somebody please help?
Thanks
When scientists first started studying electrical circuits, they didn't really know which direction the current flowed in, so they guessed it was positive to negative. However, electrons travel from negative to positive (because of their charge), so it should be the other way, but the convention stuck, and nearly everything today operates on positive to negative idea, including Fleming's Left Hand Rule. So the second finger does indeed point positive to negative. (at least, I think that's the idea behind it)

In case it's useful an easy way to remember the directions of the fingers is this: thuMb, Motion; First finger, Field direction; seCond finger, Current.
3. (Original post by Aear)
When scientists first started studying electrical circuits, they didn't really know which direction the current flowed in, so they guessed it was positive to negative. However, electrons travel from negative to positive (because of their charge), so it should be the other way, but the convention stuck, and nearly everything today operates on positive to negative idea, including Fleming's Left Hand Rule. So the second finger does indeed point positive to negative. (at least, I think that's the idea behind it)

In case it's useful an easy way to remember the directions of the fingers is this: thuMb, Motion; First finger, Field direction; seCond finger, Current.
Okay, so in an exam question for fleming's rule i would point positive terminal to negative. But what if i got a questions asking me for the direction of the flow of electrons? Do they flow from positive to negative because the negative charge of the electron repels the negative charge of the terminal?
Okay, so in an exam question for fleming's rule i would point positive terminal to negative. But what if i got a questions asking me for the direction of the flow of electrons? Do they flow from positive to negative because the negative charge of the electron repels the negative charge of the terminal?
Negative to positive. This isn't to do with the left hand rule
5. (Original post by Prussia1)
Negative to positive. This isn't to do with the left hand rule
Right, okay, thank you! To save me making a new thread, is this idea of moments correct when applied to a car......

So airbags reduces the speed of a person over a longer period of time so the momentum takes longer and the force applied to the person is therefore less??

Oh god i get so confused with momentum.... i don't know why but help would be appreciated
Right, okay, thank you! To save me making a new thread, is this idea of moments correct when applied to a car......

So airbags reduces the speed of a person over a longer period of time so the momentum takes longer and the force applied to the person is therefore less??

Oh god i get so confused with momentum.... i don't know why but help would be appreciated
On Fleming's Left Hand Rule, the question will always operate on convention, I would presume. If they make no comment on that fact, assume convention.

With airbags, I've attached a collection of mark scheme answers for AQA Unit 2 and 3, and on Unit 2 I've got an answer about seat belts, which use a similar principle to airbags. Just shift the words as appropriate. This is what I'm doing tonight for revision. Feel free to share them with others if you wish.
Attached Files
7. Physics Unit 2 Mark Scheme Answers.docx (17.2 KB, 46 views)
8. Physics Unit 3 Mark Scheme Answers.docx (16.4 KB, 43 views)
9. (Original post by Aear)
On Fleming's Left Hand Rule, the question will always operate on convention, I would presume. If they make no comment on that fact, assume convention.

With airbags, I've attached a collection of mark scheme answers for AQA Unit 2 and 3, and on Unit 2 I've got an answer about seat belts, which use a similar principle to airbags. Just shift the words as appropriate. This is what I'm doing tonight for revision. Feel free to share them with others if you wish.
Thank you so much, you've helped me beyond belief :')
10. I hope this helps: https://www.youtube.com/watch?v=whfpEeoHxNw

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