An electron is moving in a circle of radius R in a uniform magnetic field .The direction of magnetic field lines is in the downward direction inside the plane .If we instantly change the direction of magnetic fieldlines in the upward direction out of the plane .the electron :
A)will start moving in a straight line
B)will move in a circle of radius R in the same direction
C)will move in a circle of radius R in anticlockwise direction
D) will move in the same direction but in a circle of radius GREATER than R
the correct option is (D),but i'm not able to figure out why the radius is greater than R though the direction remains same by eqn: F=qvBsin(Ɵ) and Ɵ remains 180
i need explanation ,,please help !
10 points for best answer
A)will start moving in a straight line
B)will move in a circle of radius R in the same direction
C)will move in a circle of radius R in anticlockwise direction
D) will move in the same direction but in a circle of radius GREATER than R
the correct option is (D),but i'm not able to figure out why the radius is greater than R though the direction remains same by eqn: F=qvBsin(Ɵ) and Ɵ remains 180
i need explanation ,,please help !
10 points for best answer
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you must figure out the direction of force on the electron..
since the field initially is into the page
nothing was said about the direction of the motion i will assume its clockwise
F = qv x B
we know the motion will be perpendicular to the magnetic field
F = -evB
this is the magnitude of the force ...
the angle you have is incorrect the angle is between the B field and the direction of motion..since the plane of motion is perpendicular to the B field then flipping the field by 180 degs just keeps the 90 degs but it inverts the direction so that the arch wont be larger i think it will be anti clockwise this is because the force direction changes but is always perpendicular .. i think the answer you gave is incorrect I may be incorrect I am not perfect but there is nothing in the calculation that will allow for a larger R
C is the the answer but the circle will not be the same one it will be next to it like flipping the orbit over the point where it was moving when the magnetic field flipped ..
since the field initially is into the page
nothing was said about the direction of the motion i will assume its clockwise
F = qv x B
we know the motion will be perpendicular to the magnetic field
F = -evB
this is the magnitude of the force ...
the angle you have is incorrect the angle is between the B field and the direction of motion..since the plane of motion is perpendicular to the B field then flipping the field by 180 degs just keeps the 90 degs but it inverts the direction so that the arch wont be larger i think it will be anti clockwise this is because the force direction changes but is always perpendicular .. i think the answer you gave is incorrect I may be incorrect I am not perfect but there is nothing in the calculation that will allow for a larger R
C is the the answer but the circle will not be the same one it will be next to it like flipping the orbit over the point where it was moving when the magnetic field flipped ..
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remember
Radius, r= mv/qB
When, B starts reversing its direction its magnitude starts decreasing and hence, the electron inscribes a bigger circle i.e radius r increases.
When B has fully reversed its direction, then electron's radius decreases.
Hope it helped! Thank You
Radius, r= mv/qB
When, B starts reversing its direction its magnitude starts decreasing and hence, the electron inscribes a bigger circle i.e radius r increases.
When B has fully reversed its direction, then electron's radius decreases.
Hope it helped! Thank You