What Is the Ampere?

The Ampere's Rule, also known as the right-handed spiral rule, is a rule that expresses the relationship between the direction of the current and the direction of the magnetic field of the magnetic field excited by the current. Ampere's rule in energized straight wire (Ampérian rule one): Hold the energized straight wire with your right hand and let your thumb point in the direction of the current, then the four-finger pointing is the direction around the magnetic induction wire; the ampere in the energized solenoid Rule (Ampere Rule 2): Hold the energized solenoid with your right hand and let the four fingers point in the direction of the current, then the end of the thumb is the N pole of the energized solenoid.

Ampere Rule

The amperage rule of the linear current is

The force d f ₁₂ of the current element I ₁ d L ₁ on another current element I ₂ d L ₂ separated by r ₁₂ is:

d f ₁₂ = I ₂ d L ₂ × [( ₀ / 4) ( I ₁ d L ₁ × r ₁₂ / r ₁₂ ³ )]

In the formula, the directions of d L ₁ and d L ₂ are the directions of current; r ₂₁ is the radial vector pointing from I ₂ d L ₂ to I ₁ d L ₁ .

The amperage formula between current elements can be divided into two parts. One is that the magnetic field generated by the current element I ₂ d L ₂ at the current element I ₁ d L ₁ (ie, the above r ₂₁ ) is

d B = ( ₀ / 4) ( I ₂ d L ₂ × r ₂₁ / r ₂₁ ³ )

this is

French physicist discovered the magnetic effect of electric current through the famous "Aust experiment"

We usually distinguish the north and south poles of the earth through the following three methods:

Force-to-axis moment and force-to-point

According to Ampere's rule, we know that when the fingers of the right hand except the thumb are in the direction of the coil current, the thumb is pointing to the N pole. After simplification , the direction of the current in the solenoid is rotated 90 ° counterclockwise, which is the N pole of the solenoid.

There is another method, which is a converted method of Ampere's Rule . We will call it the pSqN method for the time being.

The definition of the pSqN method: when looking at the solenoid from the spiral mouth of the solenoid, if the shape is the letter "p", then the anode of the solenoid is the S pole; if the shape is "q", then the solenoid is N pole.

For the convenience of memory, pSqN can only memorize the correspondence of pS. PS itself is the abbreviation of the familiar graphic editing software Photoshop. After extensive use, it has also become a well-known verb.

Explanation:

First look for the positive electrode of the solenoid, which is where its current enters;

Then turn the solenoid over and look at the turn of the solenoid; at this time we can find that the shape of the wire wound at the turn will be similar to the lowercase "p" or lowercase "q";

If the shape is p, then the positive pole of the solenoid is the S pole, and if the shape is q, then the positive pole of the solenoid is the N pole.

This is a pSqN method for determining the solenoid.

Inverse theorem: Observe the spiral mouth of the solenoid, if it is "p", then the S pole is the positive pole of the solenoid; if it is "q", then the N pole is the solenoid Positive electrode.

The pSqN method is suitable for students to quickly determine the correspondence between the positive and negative poles of a solenoid and the N and S poles without relying on their hands in the brain when doing a question. To be sure, using Ampere's rules when doing a question can be more secure and error-free.

In addition, Amperedin can be simplified as "upper, left, bottom, and right", that is, when the magnet is placed horizontally, the current direction is from the bottom to the top, and the N pole is on the left, that is, "upper left," and vice versa. On the side is the N pole, which is "bottom right". The N pole can be quickly determined by this method.