We know that when we vary the magnetic flux in a given circuit, an induced current arises, which can be used in various appliances, such as to turn on a light bulb, heat water or make a motor work. In this way, we can say that the electrical energy of the induced current can be transformed into other forms of energy.
But apparently we don't see any modification to the initial circuit configuration, so where does this energy come from?
Answering this question, we cannot forget that we will only have an induced current when there is a variation of magnetic flux, that is, caused by an external agent, for example: the movement of a magnet or the movement of wires and turns.
The electrical energy we have comes only from movement. According to the figure below, for the loop speed to be kept constant, we have to maintain the external torque, as the induced current also creates a torque opposite to the torque applied to the spirals. In this way, if there is no external force, the spiral slows down until it stops.
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Spiral spinning in a magnetic field. Torque is required to maintain constant speed.
The possibility of converting the mechanical energy of a waterfall, or the chemical energy of coal combustion, into electrical current is the fundamental mechanism for the production of electrical energy. We call the equipment that performs this conversion generators. In fact, this equipment should be called energy converters, since they transform mechanical energy into electrical energy.
By Domitiano Marques
Graduated in Physics
Brazil School Team
Electromagnetism - Physics - Brazil School
Would you like to reference this text in a school or academic work? Look:
SILVA, Domitiano Correa Marques da. "Induced current and energy conservation"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/corrente-induzida-conservacao-energia.htm. Accessed on June 27, 2021.
