Magnetism

It doesn't. There are three things that can affect this force: another magnetic field, another conductor within the field, and the size of the gap itself, of course.

Lamination is, in essence, insulation, and anything non-magnetic and non-conductive within the field is transparent to the field itself - it's as if it weren't there.

The simple answer is that the magnetized needle is being attracted by the North Magnetic Pole (which is close to, but not the same as the geographic North Pole).

However, the colored part of the needle is not actually drawn to the North, although that would be the result of unlike charges being drawn together. The actual effect is that the needle aligns itself with the parallel lines of magnetism connecting the North and South magnetic poles, so that it lines up North and South, its northern end pointed north and its southern end pointed south.

The Earth's magnetic field is generated by the movement of its iron core in relation to the crust.
No matter where you stand on Earth, you can hold a compass in your hand and it will point toward the North Pole. What an unbelievably neat and amazing thing! Imagine that you are in the middle of the ocean, and you are looking all around you in every direction and all you can see is water, and it is overcast so you cannot see the sun... How in the world would you know which way to go unless you had a compass to tell you which way is "up"? Long before GPS satellites and other high-tech navigational aids, the compass gave humans an easy and inexpensive way to orient themselves.

But what makes a compass work the way it does? And why is it useful for detecting small magnetic fields, as we saw in How Electromagnets Work? In this article, we will answer all of these questions, and we'll also see how to create a compass from scratch!

A compass is an extremely simple device. A magnetic compass (as opposed to a gyroscopic compass) consists of a small, lightweight magnet balanced on a nearly frictionless pivot point. The magnet is generally called a needle. One end of the needle is often marked "N," for north, or colored in some way to indicate that it points toward north. On the surface, that's all there is to a compass.

The reason why a compass works is more interesting. It turns out that you can think of the Earth as having a gigantic bar magnet buried inside. In order for the north end of the compass to point toward the North Pole, you have to assume that the buried bar magnet has its south end at the North Pole, as shown in the diagram at the right. If you think of the world this way, then you can see that the normal "opposites attract" rule of magnets would cause the north end of the compass needle to point toward the south end of the buried bar magnet. So the compass points toward the North Pole.

To be completely accurate, the bar magnet does not run exactly along the Earth's rotational axis. It is skewed slightly off center. This skew is called the declination, and most good maps indicate what the declination is in different areas (since it changes a little depending on where you are on the planet).

The magnetic field of the Earth is fairly weak on the surface. After all, the planet Earth is almost 8,000 miles in diameter, so the magnetic field has to travel a long way to affect your compass. That is why a compass needs to have a lightweight magnet and a frictionless bearing. Otherwise, there just isn't enough strength in the Earth's magnetic field to turn the needle.

The "big bar magnet buried in the core" analogy works to explain why the Earth has a magnetic field, but obviously that is not what is really happening. So what is really happening?

No one knows for sure, but there is a working theory currently making the rounds. As seen on the above, the Earth's core is thought to consist largely of molten iron (red). But at the very core, the pressure is so great that this superhot iron crystallizes into a solid. Convection caused by heat radiating from the core, along with the rotation of the Earth, causes the liquid iron to move in a rotational pattern. It is believed that these rotational forces in the liquid iron layer lead to weak magnetic forces around the axis of spin.

It turns out that because the Earth's magnetic field is so weak, a compass is nothing but a detector for very slight magnetic fields created by anything. That is why we can use a compass to detect the small magnetic field produced by a wire carrying a current
The Core of our earth is molten iron, and it's spinning really friggen fast. That spin of the iron creates a large electro-magnetic field. Similar to a small bar magnet, it has two poles. The needle in the compas will be attracted to the pull of the northpole
answ2. your compass needle just aligns itself with the lines of magnetic force in your vicinity. Which in turn are influenced by the position of the poles.

because of the poles magnetic field
A compass needle aligns itself to the earth's magnetic field. The direction of the earth's magnetic extends from the earth's Magnetic South to its Magnetic North. Remember, the terms 'Magnetic North' and 'Magnetic South' refer to LOCATIONS in the Arctic and Antarctic, respectively, and not to the magnetic polarities at these locations. Because 'unlike poles attract', this means that the polarity of Magnetic North is a south pole, thus attracting the north (coloured) pole of a compass needle.
The iron core of the Earth acts like a giant bar magnet buried in the Earth.

Since that giant bar magnet is pointing South, opposites attract and the magnetized needle points North.

The strength of an electromagnet depends on the current through the coil and

the number of turns in the coil. The voltage across the coil doesn't matter at all.

So IF both of your electromagnets have the same number of turns in their coils,

then the one with 20A of current is stronger than the one with 5A of current.

If they have different numbers of turns in their coils, then we need more information

before we can decide which one is stronger.