# Skill Set 20.2

Main Page > IB Physics Skill Sets

## Contents

- 1 About this page
- 2 Problems
- 2.1 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)
- 2.2 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)
- 2.3 3. An electron travels at 3.5 x 10
^{4}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? - 2.4 4. A proton is going 1.71 x 10
^{5}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? - 2.5 5. What electric field in what direction would make the particle go straight up the page in the previous problem?

## About this page

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Table of Contents

## 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 = (18.2 A)(113 m)(.015 T)(sin 90-17)

Index: Right (East)

Middle: Forward (North)

**Thumb: UP!!!**

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### 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)

12.15 N = (4.2 A)(.121 m)(B)(sin 90)

Index: Forward (North)

Thumb: Vertical (Up)

**Middle: Left (East)**

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### 3. An electron travels at 3.5 x 10^{4} 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?

2.1 * 10^{-14} N = (1.602 * 10^{-19} C)(3.5 x 10^{4} m/s)(B)(sin 90)

B = 3.745 T

Index: Forward (North)

Thumb: Down

**Middle: Right (West)**

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### 4. A proton is going 1.71 x 10^{5} 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?

(1.602 * 10 ^{-19})(2.3 T) = (1.673 * 10 ^{-27} kg)(1.71 x 10^{5} 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.

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### 5. What electric field in what direction would make the particle go straight up the page in the previous problem?

Solution goes here