# The direction of magnetic induction – problems and solutions

1. Which of the following figures shows the correct direction of magnetic induction due to the wire carrying the electric current …

Solution

Induction of magnetic or induction magnetic field can be determined using right-hand rule.

The first way, if the electric current conductor is a straight wire then the induced magnetic field is determined in the following way: Hold the right thumb and extend the other four fingers forward and bend the four fingers into the palm of the hand. Adjust the direction of the thumb of the right hand with the direction of electric current (I). The direction of the induced magnetic field is equal to the direction of the bend of the other four fingers.

The second way, if the electric current conductor in the form of a circular wire, the induction magnetic field is determined in the following way: Hold the thumb of the right hand and spread the other four fingers forward and bend four fingers into the palm of the hand. Adjust the direction of the four fingers of the right hand with the direction of electric current (I). The direction of the induced magnetic field is equal to the direction of the thumb.

Now apply the right-hand rule to each answer.

Answer A: Using the right-hand rule in a first way, this answer is true.

Answer B: Using the right-hand rule in a first way, this answer is wrong. Why wrong? Circles and x marks mean the direction of the induced magnetic field away from the reader (perpendicular to the paper field), whereas the circle and the black circle mean the direction of the magnetic field near the reader (perpendicular to the outer field of paper). If the right-hand rule is applied then the circle and the black circle must be at the top representing the direction of the magnetic field approaching the reader, while the circle and the x should below represent the direction of the magnetic field away from the reader.

Answer C: Using the right-hand rule in a second way, this answer is wrong.

Answer D: Using the right-hand rule in a first way, this answer is wrong (similar to answer B).

Answer E: Using the right-hand rule in a first way, this answer is wrong (similar to answer B).

2. If O states the direction of magnetic induction perpendicular to the outer paper and X states the direction of magnetic induction perpendicular to enter the paper field, then the correct figure is …..

Solution

The direction of the induced magnetic field or the direction of magnetic induction can be determined using the right-hand rule, as in the previous problem.

Answer A: Using the right-hand rule, this answer is wrong.

Answer B: Using the right-hand rule, this answer is wrong.

Answer C: Using the right-hand rule, this answer is correct.

Answer D: Using the right-hand rule, this answer is wrong.

Answer E: Using the right-hand rule, this answer is wrong.

3. If O = the perpendicular direction exits the paper plane and X = the direction perpendicular to the paper field, then the following figure which shows the correct direction of magnetic induction around the electrically conductive wire is …

Solution

The direction of the induced magnetic field or the direction of magnetic induction can be determined using the right-hand rule, as in the previous problem.

Answer A: Using the right-hand rule, this answer is wrong.

Answer B: Using the right-hand rule, this answer is wrong.

Answer C: Using the right-hand rule, this answer is correct.

Answer D: Using the right-hand rule, this answer is wrong.

Answer E: Using the right-hand rule, this answer is wrong.