# IB Physics Design Lab - Does the temperature a bar magnet is exposed to affect the magnetic field strength of the bar magnet?

by venky1998 (student)

Physics Design Lab – Magnetism

Research Question: Does the temperature a bar magnet is exposed to affect the magnetic field strength of the bar magnet?

Background Information: We have learned that at high temperatures, the atoms in a metallic bar magnet start to vibrate faster, in a random manner. This causes the magnetic domains in the bar magnet to lose their orientation, further leading to the domains not being in the same direction, as they were previous to heating. As the domains lose their orientation, they cancel out each other’s magnetic field, leading to an overall weaker magnet. This explanation leads to the theory that heating is a means of demagnetization, which we learned in lower classes. On the other hand, cooling a magnet leads to the borders of the domain to move ever so slightly to lead to a further preferential state (and orientation), thus leading to the formation of an even stronger bar magnet. This leads to the conclusion that cooling is a means of increasing magnetic field strength. This investigation will look to test these two theories, and in general, look to find a trend between the temperature of a magnet and its magnetic field strength. This is a very important part of our lives, as in the future we look to create ‘super-magnets’ at 0K which are extremely strong.

Hypothesis: It can be hypothesized that at higher temperatures, due to the disorientation of magnetic domains, the magnetic field strength of the bar magnet will decrease, whereas at lower temperatures, due to a more preferential orientation of magnetic domains, the magnetic field strength of the bar magnet will increase. In all, as the temperature increases, it can be hypothesized that the magnetic field strength will decrease.

Independent Variable: Temperature the bar magnet is exposed to. This will be changed by placing the bar magnet in a water bath of the temperature required (0, 20, 40, 60, 80 and 100°C), for a specific period of time. The temperature of the bar magnet will be measured using a digital thermometer before the experimentation, to ensure it has reached the desired temperature, so as to get accurate results.                                                               ...