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# Flemings left hand rule HARD QUESTION watch

1. https://tavistockcollegescience.wiki...Electromag.pdf
For question 1aii on the above link, how do work out the direction of the force? i tried using flemings left hand rule and it keeps giving me the opposite direction
2. (Original post by haron1)
https://tavistockcollegescience.wiki...Electromag.pdf
For question 1aii on the above link, how do work out the direction of the force? i tried using flemings left hand rule and it keeps giving me the opposite direction
Lorentz force is given by

Using the right hand rule the resultant vector from v x B points upwards: now remember the charge is -e
so which points downwards
3. (Original post by haron1)
https://tavistockcollegescience.wiki...Electromag.pdf
For question 1aii on the above link, how do work out the direction of the force? i tried using flemings left hand rule and it keeps giving me the opposite direction
Remember that the direction of conventional current is opposite of the electron flow
4. (Original post by PhysicsMathsTut)
Remember that the direction of conventional current is opposite of the electron flow
ok i know that but looking at the question as it is on the paper- the first finger of my left hand is pointing into the paper, my thumb is pointing right and second finger down. Since the 2nd finger points down the conventional current is downwards so the electron feel a force upwards?
5. (Original post by haron1)
ok i know that but looking at the question as it is on the paper- the first finger of my left hand is pointing into the paper, my thumb is pointing right and second finger down. Since the 2nd finger points down the conventional current is downwards so the electron feel a force upwards?
Thumb shows the direction of the force on the electrons. Second finger is current, it should point left

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6. It's Towards Q, use flemming's right hand rule.
7. (Original post by PhysicsMathsTut)
Thumb shows the direction of the force on the electrons. Second finger is current, it should point left

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why should the second finger point left- the electrons don't flow that way(current)?
8. (Original post by haron1)
why should the second finger point left- the electrons don't flow that way(current)?
The electrons flow as a result of the force on them. You're asked about the force. Because of the movement of the plane, each electron is moving right. That's current to the left when you're using Fleming's LHR

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9. (Original post by PhysicsMathsTut)
The electrons flow as a result of the force on them. You're asked about the force. Because of the movement of the plane, each electron is moving right. That's current to the left when you're using Fleming's LHR

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thanks
10. the first finger (magnetic field, as shown by the X's and the arrow pointing right) should point right. the thumb (force) is then pointing upwards, the correct answer

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