Chapter 36, Problem 22A

Three pairs of electromagnets made with identical iron cores are shown below. Note the number of turns of wire, each of which carries the same current.

a. Rank the electromagnet pairs A, B, and C in terms of the force between the electromagnets, from most attractive to most repulsive.

b. Rank the electromagnet pairs A, B, and C in terms of the magnitude of the magnetic field at the exact midpoint between the electromagnets.

To determine

To Find: the rank of the electromagnet pairs A, B, and C in terms of the force between the electromagnets, if electromagnets are made with identical iron cores having several turns of wire and the same passing current. 

Answer to Problem 22A

The rank is B, C, A

Explanation of Solution

Introduction: 

An electromagnet is a magnet in which the magnetic field exists when current passes through a conducting wire wrapped around an iron core.

Explanation: 

The magnetic field is produced by an electric current. The magnetic field surrounding a bar magnet is shown by drawing the magnetic lines of force. Opposite poles of a magnet attract. The number of turns on the coil generates a strong field of attraction/repulsion.

So, in the given figure A, B, and C iron cores A and B have the same number of turns but their orientation is different. With the orientation of iron cores, the iron core A has strong repulsive (like poles), B has strong attractive (unlike) and C has again repulsive (like). The rank would be strongly attractive to strong repulsive as B, C, and A.

Conclusion: 

Considering the number of turns on the iron core and their orientation concerning poles, the rank would be B, C, and A.

To determine

To Find: The rank of the electromagnet pairs A, B, and C if electromagnets are made with identical iron cores having several turns of wire passing with same current. 

Answer to Problem 22A

The rank is B, A = C.

Explanation of Solution

Introduction: 

The magnetic field depends on

• the current passing through the conductor
• The distance of the point from the conductor.

More the current pass, more is the magnetic field.

Explanation: 

The magnetic field can be generated due to electric current passing through conductor. So, if electric current is increased magnetic field also increases. Magnetic field also depends upon the core material.

According to the given figure, iron cores A and B are having equal number of turns in them. But the orientation is different resulting in different magnetic fields for both cases.

Since, iron cores A and C are having like poles, so iron cores A and C will have zero magnetic field. And, iron core B is having the unlike poles, so it has a stronger magnetic field than the other two. Hence, the ranking is given as B, A = C.

Conclusion: 

Hence, according to the number of turns and orientation of the magnetic field, the electromagnets are ranked as B, A = C.