When either an AC or DC current is passed over a metal rod, which one current (AC or DC) will make the rod magnetic.I did the experiment once but cant remember the results
The answer is DC or direct current. By passing electric current The best method of making a powerful magnet is by passing electric current. Wind a length of an insulated copper wire around a steel rod DY and connect it to a battery and a switch. After the current has passed through the coil for some time you will notice that the steel rod gets magnetized. The polarity of the rod depends upon the direction of the current. If the bar is viewed from one end and the current is found to be flowing in a clockwise direction, then that end will become a south pole and if the current is flowing in the anticlockwise direction then that end will be a north pole.
THAT doesn't make any difference. I assume you're talking about making a metal rod (which has to be iron really) an electromagnet by wrapping it around an active wire? The type of current in the wire doesn't make a difference here. Only if it's AC, the direction of the magnetic field around the wire will be different - constantly changing. AC current is always generated by generators and is always used in transformers. DC current has to be used in electric motors and split-ring commutators and carbon brushes allow the coil of wire to rotate continuously.
To magnetize a steel rod, only DC can do it. AC will demagnetize the metal rod. If you only want a very short term magnet, ie not permanent, both will create a magnetic field but does not magnetize the rod. When a ferromagnetic material is exposed to an external magnetic field and then removed from the field, the material can retain some of the field. This effect is known as hysteresis--the material retains a magnetic field. At this point, the material has been magnetized. There are several ways to magnetize an item. If an item is placed into the center of a coil of wire, and then a large amount of DIRECT CURRENT is sent through the wire, the item can be magnetized. The orientation of its poles will match the orientation of the field generated by the coil. Permanent magnets can be demagnetized by placing the magnet in a solenoid which has an ALTERNATING CURRENTbeing passed through it. The ALTERNATING CURRENT will disrupt the long range ordering, in much the same way that direct current can cause ordering.
