Lecture%2022B

# Lecture%2022B - Physics 1B Lecture 22B X X X X X X X X X X...

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Unformatted text preview: Physics 1B Lecture 22B X X X X X X X X X X X X X X X X X X X X Step 2 Example An electron travels at 2.0x10 7 m/s in a plane perpendicular to a 0.10T large uniform magnetic field directed into the screen as shown below. Describe its resulting path (both magnitude and direction). Answer First, you must define a coordinate system. Let’s say the original direction of motion of the electron as the positive x-direction. B field v- Step 2 Answer This means that the electron will eventually be moving ownward in the magnetic field. X X X X X X X X X X X X X X X X X X X X B field v- Now, which direction will it feel a force? Via RHR1, it will feel a orce to the left (don’t orget to flip the vector at he end). This will keep on occurring until it completes one circular loop (and then it keeps repeating). So, the resulting path will be circular (clockwise) as the agnetic force causes centripetal acceleration. Step 2 Answer To find the magnitude, use Newton’s 2nd Law with the agnetic field causing a centripetal acceleration. e know all of the variables (e and m e can be looked up). F ∑ = ma F B = ma c qvB sin θ = m v 2 r qB 1 ( ) = m v r r = mv qB r = 9.11 × 10 − 31 kg ( ) 2.0 × 10 7 m s ( ) 1.60 × 10 − 19 C ( ) 0.10T ( ) = 1.1 × 10 − 3 m In the previous example, f the electron’s original elocity was not erpendicular to the agnetic field, then the esulting path with will be piral. This spiral path is called a elix....
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Lecture%2022B - Physics 1B Lecture 22B X X X X X X X X X X...

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