Global Journal of Science Frontier Research, A: Physics and Space Science, Volume 22 Issue 1

resistivity is inversely proportional to the mean free path or the average distance that a particle travels between successive shocks that at a certain temperature is limited by the thermal vibrations of the atoms (Zední ček, Kühl & Primavesi, 2021). On the other hand, the relationship between resistivity and resistance is shown below: (14) If the length and cross-section remain constant, simplify the equation to: (15) Therefore, in (12) ρ and ρₒ can be replaced by R and R ₒ , respectively: (16) III. E xperiment A brief summary of the experiment carried out will be made hereafter to enlighten the reader about how to try to find the relationship between the dependent and independent variables. To begin with, an electromagnet, which consists of a coil of wire wound in a ferromagnetic material, is connected to the direct current after being heated to temperatures higher than that of the ambient and lower than 333.15 K. Specifically, this limit was determined to avoid the risk of burns and thus guarantee the safety of the experiment. Subsequently, a steel nut is brought close to the electromagnet so that it attracts it. The current provided to the electromagnet is reduced by manually decreasing the potential difference between the terminals, in order to observe at what voltage the electromagnet no longer provides the retaining force that holds the nut and the screw together. In this way, it is intended to confirm the hypothesis that the decrease in current caused by the increase in resistance after heating of the electromagnet, generates a reduction in the magnetic flux and, therefore, also in its force. a) Key variables i. Constants Table 1 : Identification and analysis of controlled variables Controlled variable Why is it constant? Nut Features • material • mass • position relative to the winding An object whose material was magnetized in the presence of a magnetic field was sought in order to measure how the magnetic effects of the electromagnet change at different temperatures, such as steel. Winding characteristics ● geometry • core material • cable gauge At first, it was considered to use nuts of different masses as a parameter to determine the strength of the magnet. But this idea was discarded, as there was a possibility that the nuts could be positioned differently. This would be a source of error because the intensity of the magnetic field changes in different parts of the electromagnet, as explained in the next point. The position of the nut was kept constant because the intensity of the magnetic field is greatest near the poles of the electromagnet and even greater within it. However, in this particular experiment, the internal part is not taken into account because a hollow electromagnet is not used. Relationship between Temperature and the Holding Force of an Electromagnet in a Changing Magnetic Field © 2022 Global Journals 1 Year 2022 14 Global Journal of Science Frontier Research Volume XXII Issue ersion I VI ( A ) R = Rₒ(1+α (T - Tₒ)) This section specifies the characteristics of the variables included in the experiment and the reasons that account for them being kept under control or being allowed to change.