# Skill Set 21.2

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Main Page > IB Physics Skill Sets > Skill Set 21.2

## Contents

- 1 About this page
- 2 Problems
- 2.1 1. A loop or wire with a radius of 0.78 m is in the plane of this page, and is rotated so that the loop forms a 23.0 degree angle with the page. If there is a 3.72 T magnetic field into the page, and the rotation takes .015 s, what is the average EMF generated? Which way does it flow?
- 2.2 2. The wire below is 2.28 m long (really!) and is traveling through a 6.71 T magnetic field out of the page. What is its speed if there exists a potential of 41.6 V from one end to the other? Label the positive end of the wire.
- 2.3 3. A transformer has 350 primary windings, and 1600 secondary windings. What is the voltage in the primary if there is a voltage of 512 V (AC) in the secondary?
- 2.4 4. You want to step 120 VAC down to 9.6 VAC with a transformer. What should be the number of secondary windings if you have 1800 primary windings?
- 2.5 5. A transformer steps 240 VAC down to 1.5 VAC. What current flows in the secondary if the primary side has 2.6 A flowing through it?

## About this page

All images uploaded for this page must start with the string "Skill_Set_21.2_" so the image 16-38.jpg associated with chapter 16 should be uploaded as Skill_Set_21.2_16-38.jpg. This way we can avoid conflicts in the image directory, and we can find images easily.

Table of Contents

## Problems

### 1. A loop or wire with a radius of 0.78 m is in the plane of this page, and is rotated so that the loop forms a 23.0 degree angle with the page. If there is a 3.72 T magnetic field into the page, and the rotation takes .015 s, what is the average EMF generated? Which way does it flow?

E = ((3.72 T)*((.78 m)^{2} * 3.14) * (cos 23 - cos 0) / .015 s

Table of Contents

### 2. The wire below is 2.28 m long (really!) and is traveling through a 6.71 T magnetic field out of the page. What is its speed if there exists a potential of 41.6 V from one end to the other? Label the positive end of the wire.

E = B * v * L

41.6 V = (6.71 T) * v * (2.28 m)

### 3. A transformer has 350 primary windings, and 1600 secondary windings. What is the voltage in the primary if there is a voltage of 512 V (AC) in the secondary?

(V

_{p}/ V_{s}) = (N_{p}/ N_{s})

(V_{p}/ 512 V) = (350 / 1600)

V_{p}= 112 V

### 4. You want to step 120 VAC down to 9.6 VAC with a transformer. What should be the number of secondary windings if you have 1800 primary windings?

(V

_{p}/ V_{s}) = (N_{p}/ N_{s})

(120 V / 9.6 V) = (1800 / N_{s})

N_{s}= 144

### 5. A transformer steps 240 VAC down to 1.5 VAC. What current flows in the secondary if the primary side has 2.6 A flowing through it?

(V

_{p}/ V_{s}) = (I_{s}/ I_{p})

(240 V / 1.5 V) = (I_{s}/ 2.6 A)

I_{s}= 416 A