臺灣國際科展

芯電感應

科展類別
臺灣國際科展
屆次
2005年
科別
物理科
學校名稱
國立臺南女子高級中學
作者
郭惠斐、徐維妤
關鍵字
安培定律,螺線管,感應磁場

摘要或動機

Based on Ampere,s Law, the magnetic field intensity of the solenoids is B=μ0μr?n?I, where μ0 is the magnetic permeability of free space, μr is the relative magnetic permeability, n is the number of coils per unit length and I is the solenoidal current. The end magnetic field of the solenoid must multiply by one half. According to the above result, it can be greatly strengthened by the addition of a ferromagnetic core. First, we observe three different inserted materials of coils (wood, iron and magnetite), whose magnetic induction in different solenoidial current. By experiment, when the iron and magnetite materials were inserted into the coil, it would produce larger magnetic induction. The calculated relative magnetic permeabilities of wood, iron and magnetite materials are 0.57, 18.37 and 18.32, which are close to the reported paper (1). When the driving field is removed, the fraction of the saturation magnetization of the magnetite is retained, which is called hysteresis and is related to the existence of magnetic domains in the material. In the second part, we change the frequency of circuit switch, which induced different current. Compared with the result of the first part, it would fit the result, which is the induced magnetic field is proportion to the solenoidal current. 根據安培定律,螺線管的磁場為B=μ0μr?n?I。其中μ0為真空中的導磁率,μr為相對的導磁率,n為單位長度的線圈匝數,I則為通入螺旋管的電流。至於螺旋管的端點磁場須再乘上1/2。所以根據上述的結果,當螺旋管插入鐵磁性物質,會增強螺旋管的磁場。首先,觀察三種不同的芯物質;非鐵磁性材料,軟磁材料,硬磁材料(木棒,低碳鋼棒,磁鐵棒)在不同的外加磁場下的感應磁場,得到芯物質的磁化曲線,而計算出來的相對導磁率分別為0.57, 18.37 和18.32與參考文獻(1)接近。而當外加磁場移走時,硬磁性物質的磁性仍然存在,稱為殘磁現象。在第二部分,我們改變線路開關的頻率。發現不同的開關頻率,會得到不同的螺旋管電流,而造成不同的感應磁場。再度驗證了感應磁場大小是正比於螺旋管電流的大小。


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