Magnetic Force and Electric Current
You mean electric current causes a magnetic substance to be magnetized?When there is an electric current through a wire or rod as shown in Figure 5, a circular magnetic force is created, which can be mathematically analyzed. You can observe this, if you perform the experiment in Figure 6. (I have not tried it.)
If charges flow due to electric field, what flows when there is a magnetic field?
If charges are present in the magnetic field, the magnetic field can affect them.
You stated that flow of charges can create magnetic field. You also state that magnetic field affects the charges? Is this an egg or chicken dilemma?
I understand your confusion. The flow of charges induces magnetic field and then affected by the magnetic field they induced. That is what I said. The details and mathematics of how both interact is more involved, and will be discussed later.
Consider slightly different case where there is a magnetic field as in Figure 10. Then, the force created by the field is mathematically defined as F=qVxB, where F is the force induced by the charge, q is the charge flowing, V is the velocity of the charge flowing, and B is the strength of the magnetic field or magnetic field density. If charges flow in the wire down up then the wire moves left, and when charges flow up down the wire moves right. Here the magnetic field induced by the current it self is ignored.
How does magnetic field affect, if we bring a conducting wire near as in Figure 7?
I suppose you ask whether the charges will flow to light up the bulb. Magnetic field does not attract or repel stationary charges.
A magnetic force is experienced or induced only by a moving or flow of charge. That is there must be electric current for magnetic force to be induced.
Let me, get back at an earlier question. You stated that when there is current in a rod, magnetic field is created as in figure 6. Does that mean that the wire that is conducting the current has become a magnet?
Yes. But the strength of the magnetic field would be small and magnetic field will collapse soon after the current stop flowing.
How can we measure the magnetic field strength?
"Magnetic flux density or concentration of flux lines at a point determines the amount of magnetic force."
Mathematically, total flux lines passing through a given area A is Phi or sometimes expressed as Psi.
B = magnetic flux density = concentration of flux lines
B = # of lines of force / Area
B=Phi / A
The units of the expression are as follows;
Tesla = Weber/ m2 = 108 lines/ m2
How is the amount of flux lines and magnetic forces related?
Greater the flux lines, greater the flux density, the greater the force; of course, the magnetic force is proportional to work or energy that can be gained.
Does the direction of the current flow affect the magnetic field? Why?
Yes, that's how it is or due to nature of it. Consider the case in Figure 9; The core becomes magnetized as the charges flow. The strength of the magnetization of the core among other factors depends on the type of material, and the amount of current passing through the coil.
Can you explain how the coil around the core results in core being magnetized as north pole and south pole?
I have not thought through the details. But, consider a small potion of the coil in Figure 12. If it is very small then it is lie a wire, and magnetic field surrounds it when there is current. "These little whirls of magnetic force combine to produce one large field (North to South) that surrounds the entire coil."
Why is rod becoming magnetized when changing current passes through is important?
The rod becoming magnetized as the changing current passes through leads to inductance, which is an important electromagnetic property.
What is inductance?
(Continuous Question)