30.1
Electromagnetic induction is produced when an electrically conducting material is exposed to a time-varying magnetic field.
For example, consider a bar magnet placed close to a coil. The galvanometer connected to this coil shows zero current passing through it.
If the bar magnet moves toward the coil, a current flows through the coil. Furthermore, if the bar magnet is moved away from the coil, current flows in the opposite direction.
Similarly, if the bar magnet is kept fixed and the coil is moved in either direction, then current flows through the coil.
Suppose a bar magnet is replaced with a second coil connected to a battery. If one of the coils is moved, a current flows through the other coil.
If a switch controls the current passing through the one coil, then an instantaneous current pulse is induced in the other coil while opening or closing the switch.
Here the current flowing through the other coil is called an induced current, and the corresponding emf is called an induced emf.
当通过将条形磁铁推入或推出线圈而改变线圈中的磁场时,就会产生电动势。 相反方向的运动会产生符号相反的电动势,并且磁极反转也会反转电动势的方向。 如果移动线圈而不是磁铁,也会产生相同的结果——重要的是相对运动。 运动越快,电动势越大。 此外,当磁铁相对于线圈静止时,不存在电动势。
使用两个电路可以产生类似的效果,其中一个电路中的电流会在附近的第二个电路中感应出电流。 例如,如果载流电路移向或远离另一个固定电路,则在另一个电路中会感应出电动势。 此外,如果第一个电路中的电流通过开关控制,则开关的打开和关闭会在另一个电路中感应出电动势。
在上述所有情况下,感应电动势都会感应出电流,称为感应电流。 所有这些观察结果的共同因素是磁通量的变化。 在这里,磁通量正在变化,要么是因为磁场与时间相关,要么是因为电路的运动改变了通过它的磁通量。 感应的发生是由于所涉及的力的非静态性质。 在分析由电荷分布产生的静电场和由时变磁场产生的非静电场时必须仔细考虑。
Electromagnetic induction is produced when an electrically conducting material is exposed to a time-varying magnetic field.
For example, consider a bar magnet placed close to a coil. The galvanometer connected to this coil shows zero current passing through it.
If the bar magnet moves toward the coil, a current flows through the coil. Furthermore, if the bar magnet is moved away from the coil, current flows in the opposite direction.
Similarly, if the bar magnet is kept fixed and the coil is moved in either direction, then current flows through the coil.
Suppose a bar magnet is replaced with a second coil connected to a battery. If one of the coils is moved, a current flows through the other coil.
If a switch controls the current passing through the one coil, then an instantaneous current pulse is induced in the other coil while opening or closing the switch.
Here the current flowing through the other coil is called an induced current, and the corresponding emf is called an induced emf.
From Chapter 30:
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