i need helping answering this homework question on magnetism:
which of the following will induce a current in a nearby circuit?
A. any magnetic field
B. an electromagnet with varying current
C. an unchanging electromagnet
D. a powerful, unmoving horseshoe magnet
To determine which of the given options will induce a current in a nearby circuit, we can refer to Faraday's law of electromagnetic induction. According to this law, a changing magnetic field can induce an electric current in a conducting circuit.
Let's analyze each option:
A. Any magnetic field: A static magnetic field alone cannot induce a current in a circuit unless it is changing. Therefore, option A is incorrect.
B. An electromagnet with varying current: This option involves an electromagnet, which is essentially a coil with an iron core. By varying the current in the coil, the magnetic field strength around it changes. This changing magnetic field can induce a current in a nearby circuit, as per Faraday's law. Therefore, option B is correct.
C. An unchanging electromagnet: An unchanging electromagnet produces a static magnetic field that does not vary. As mentioned earlier, a static magnetic field cannot induce a current in a circuit. Thus, option C is incorrect.
D. A powerful, unmoving horseshoe magnet: Similar to option C, a powerful, unmoving horseshoe magnet produces a static magnetic field, which does not induce a current in a circuit. Therefore, option D is incorrect.
In summary, the correct option is B. An electromagnet with varying current will induce a current in a nearby circuit, based on Faraday's law of electromagnetic induction.