Question

What is the purpose of a dedicated coil that has the ability to select certain coil elements?

1) To increase the efficiency of the coil
2) To decrease the resistance of the coil
3) To control the flow of current in the coil
4) To generate a magnetic field in the coil

Answer 1

Option 3. is correct. The purpose of a coil with selectable elements is to control the flow of current, optimizing the performance of devices that use electromagnetism. Faraday's experiments demonstrated that more coil turns result in greater induced emf. A copper ring in a magnetic field induces an electric field and current, unlike a wooden ring.

Step-by-step explanation:

The purpose of a dedicated coil that has the ability to select certain coil elements is to control the flow of current in the coil. This feature allows for more precise manipulation of electromagnetic fields and, depending on the application, can improve the efficiency of devices such as transformers, motors, and generators. By selecting specific elements within the coil, the magnetic field can be tailored to the required specifications for a given application, thereby optimizing the device's performance.

The magnitude of the force on the magnet, when a magnet is thrust into a loop of wire, depends on the induced current in the loop and hence on the resistance of the loop. According to Lenz's Law, the force on the magnet is always such as to oppose the change in magnetic flux that produced it. The greater the resistance, the smaller the induced current, and hence, the smaller the force exerted by the coil on the magnet.