- #1
chris69
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Hello everyone,
I have two different problems from webassign homework that I could use some clarification with; as stated in the title, I'm having trouble applying the right hand rule in both. Since the basis of my difficulties are the same, I hope it's okay to include both problems in the same thread. Here's how I've learned the right hand rule, I'm hoping it's correct:
Thumb = Direction of electric charge/current/velocity vector/propagation of wave
Fingers, pointed outward forming a 90° angle with thumb = Direction of magnetic field vector
Palm, facing outward = Direction of Lorentz force vector/electric field
1.) A 2.10 m length of wire is held in an east-west direction and moves horizontally to the north with a speed of 15.3 m/s. The vertical component of Earth's magnetic field in this region is 40.0 µT directed downward. Calculate the induced emf between the ends of the wire and determine which end is positive.
2.) Consider an electromagnetic wave traveling in the positive y-direction. The magnetic field associated with the wave at some location at some instant points in the negative x-direction as shown in the figure below. What is the direction of the electric field at this position and at this instant?
Figure: https://www.webassign.net/sercp9/21-mcq-001.gif
None
#1. The answer to the bolded part of the question is the west end is positive. The wire is moving upwards, so my thumb goes upwards. Since the magnetic force of the Earth is going downward, I would think I would point my fingers downward, but since this is not anatomically possible does downward entail pointing my fingers in the negative direction on the z-axis/fingers into the screen? Thus, my palm would be facing west, and the west end is positive. Is my understanding right here?
#2. The answer is the negative z-direction. Thumb goes to the right on the y-axis in direction of the propagation vector (c), B-field/fingers goes into the screen in the negative x direction, and so my palm is facing up in the positive z-direction...However, this is not the answer. What am I doing wrong?
Thanks!
I have two different problems from webassign homework that I could use some clarification with; as stated in the title, I'm having trouble applying the right hand rule in both. Since the basis of my difficulties are the same, I hope it's okay to include both problems in the same thread. Here's how I've learned the right hand rule, I'm hoping it's correct:
Thumb = Direction of electric charge/current/velocity vector/propagation of wave
Fingers, pointed outward forming a 90° angle with thumb = Direction of magnetic field vector
Palm, facing outward = Direction of Lorentz force vector/electric field
Homework Statement
1.) A 2.10 m length of wire is held in an east-west direction and moves horizontally to the north with a speed of 15.3 m/s. The vertical component of Earth's magnetic field in this region is 40.0 µT directed downward. Calculate the induced emf between the ends of the wire and determine which end is positive.
2.) Consider an electromagnetic wave traveling in the positive y-direction. The magnetic field associated with the wave at some location at some instant points in the negative x-direction as shown in the figure below. What is the direction of the electric field at this position and at this instant?
Figure: https://www.webassign.net/sercp9/21-mcq-001.gif
Homework Equations
None
The Attempt at a Solution
#1. The answer to the bolded part of the question is the west end is positive. The wire is moving upwards, so my thumb goes upwards. Since the magnetic force of the Earth is going downward, I would think I would point my fingers downward, but since this is not anatomically possible does downward entail pointing my fingers in the negative direction on the z-axis/fingers into the screen? Thus, my palm would be facing west, and the west end is positive. Is my understanding right here?
#2. The answer is the negative z-direction. Thumb goes to the right on the y-axis in direction of the propagation vector (c), B-field/fingers goes into the screen in the negative x direction, and so my palm is facing up in the positive z-direction...However, this is not the answer. What am I doing wrong?
Thanks!