# Skill Set 20.2

All images uploaded for this page must start with the string "Skill_Set_20.2_" so the image 16-38.jpg associated with chapter 16 should be uploaded as Skill_Set_20.2_16-38.jpg. This way we can avoid conflicts in the image directory, and we can find images easily.

## Problems

### 1. 18.2 A of current flow east along a wire in a magnetic field of 0.0150 T that is 17.0 degrees east of North. What force acts on the wire if it is 113 m long? (Magnitude and direction) $F = ILB sin \ \Theta$

F = (18.2 A)(113 m)(.015 T)(sin 90-17) $F \approx\ 29.5 N$

Index: Right (East)
Middle: Forward (North)
Thumb: UP!!!

### 2. A 4.2 Amp current flows North in a wire that is 12.1 cm long. What is the magnetic field (Assume it is perpendicular) if the wire experiences a vertically upward force of 12.15 N? (Magnitude and direction) $F = ILB sin \ \Theta$

12.15 N = (4.2 A)(.121 m)(B)(sin 90) $B \approx\ 24 T$

Index: Forward (North)
Thumb: Vertical (Up)
Middle: Left (East)

### 3. An electron travels at 3.5 x 104 m/s to the North, and experiences a force of 2.1 x 10-14 N vertically downward. What is the magnitude and direction of the magnetic field exerting this force? $F = qvB sin \ \Theta$

2.1 * 10-14 N = (1.602 * 10-19 C)(3.5 x 104 m/s)(B)(sin 90)

B = 3.745 T $\approx 3.7 T$

Index: Forward (North)
Thumb: Down
Middle: Right (West)

### 4. A proton is going 1.71 x 105 m/s in the plane of the page in a 2.30 T magnetic field out of this page. What is the radius of its path? Which direction does it circle, ACW or CW? $\ qB = mv / r$

(1.602 * 10 -19)(2.3 T) = (1.673 * 10 -27 kg)(1.71 x 105 m/s) / (r)

r = 7.76 * 10 -4 m

Magnetic Field is coming out of the page so to oppose the field is to have the Magnetic Field going back into the page. Use one of the right hand laws (the one that has just your thumb) to show that the direction of the electron is CW.