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早在霍尔(E.H.Hall)发现以他的名字命名的磁场电效应之前很久,人们已经知道,载流导体的电阻随所用磁场变化。这个现象系于1856年为汤姆逊(W.Thomson)所发现,以后又以所谓高斯效应为人们知悉;然而和霍尔效应一样,在几十年内在技术上都没有很大意义。只有铋的电阻随所用磁场的变化这一点或许有些实际意义:一只扁平的双极铋卷线的磁阻,当磁感应B=1T(泰斯拉)(1T≈10~4G)时,其值增加到采用磁场前电阻值的一点五倍。以后每增加0.1T,阻值还进一步线性变化达4～5％。因而只有铋探头能用来测量很强的磁场。
Long before E.H.Hall discovered the electric field effect named after him, it is known that the resistance of the current-carrying conductor varies with the magnetic field used. This phenomenon was discovered by W.Thomson in 1856 and later known by the so-called Gaussian effect. However, as with the Hall effect, it has not been technologically significant for decades. Only the change in the resistance of bismuth with the applied magnetic field may be of some practical significance: the reluctance of a flattened bipolar bismuth wire with a magnetic induction of B = 1T (Tesla) (1T≈10 to 4G) Increased to 1.5 times the resistance value before using the magnetic field. After each additional 0.1T, the resistance also further linear changes of 4 ~ 5%. Only bismuth probes can therefore be used to measure strong magnetic fields.