Practice on Faraday's Law, also known as the law of electromagnetic induction. Take the opportunity to clarify your doubts with the commented resolutions.
Question 1
A magnetic flux passes through a loop, initially with 6000 Wb and, 2 seconds later, with 2000 Wb. In this case, determine the induced electromotive force.
Answer: 2000V
The electromotive force is the ratio between the variation of magnetic flux over time.
Replacing the values in the formula:
Question 2
To obtain an electromotive force with a value of 4 V in a time interval of 5 seconds, what must be the change in magnetic flux?
Answer: 20 Wb
The modulus of the electromotive force is related to the variation of the magnetic flux through the equation:
Thus, the magnetic flux will be:
The negative sign indicates that the change in magnetic flux occurs in the opposite direction to the change that would generate the positive EMF.
Question 3
Suppose that a closed circuit composed of a coil (winding of conductive wire in the form of turns) is connected to an ammeter. A magnet is arranged inside the coil. Both magnet and circuit can move, but only in the same direction. Evaluate the following statements and identify the only one in which there will be no electric current.
a) The ammeter will show a current reading if the magnet approaches the coil, kept fixed.
b) The ammeter will show a current reading if the coil approaches the magnet, kept fixed.
c) The ammeter will show a current reading if the magnet and the coil both move, in opposite directions and at the same speed.
d) The ammeter will show a current reading if the magnet and the coil both move, in the same direction, and at the same speed.
According to Faraday's law, a current is formed when a magnet moves through a loop, where the relative movement between them produces a variation in the magnetic field.
Thus, if both move in the same direction and at the same speed, there is no relative movement, therefore, no variation in the magnetic flux, producing no current.
Question 4
(EEAR 2016) Correctly associate the laws of electromagnetism with the statements described below: ( ) Faraday's Law ( ) Lenz's Law ( ) Ampere's Law.
I. “The direction of the electric current induced by the variation of the magnetic flux in a closed circuit is such that its effects tend to oppose the variation in the flux that gave rise to it”.
II. “For an infinite straight conductor carried by an electric current of intensity i, the magnitude of the magnetic field vector B in a point P, which is at a distance r from this conductor, will be inversely proportional to the distance r and directly proportional to i”.
III. “The electromotive force induced in a loop is directly proportional to the variation in the magnetic flux that passes through it and inversely proportional to the time interval in which this variation occurs”. Of the alternatives below, the correct one is:
a) I – II – III
b) II – III – I
c) III – I – II
d) III – II – I
Question 5
(UFRN 2010) The Englishman Michael Faraday (1791 – 1867) can be considered one of the most influential scientists of all time and his scientific works still have repercussions on society today scientific-technological. One of the most important of these works is the law of electromagnetic induction that bears his name – Faraday's Law –, which deals with an experimental situation involving the magnet and a loop. This Law can be stated as: “the electromotive force induced in a closed loop is proportional to the variation of the magnetic flux that crosses it and inversely proportional to the time interval in which this occurs. variation".
In relation to the Law referred to in the text, it is correct to state that the electromotive force induced in the loop
a) depends on the product of the variation of the magnetic flux through the loop and the time interval.
b) does not depend on the relative movement between the magnet and the loop.
c) depends on the relative movement between the magnet and the loop.
d) does not depend on the ratio between the variation of the magnetic flux through the loop over the time interval.
It is precisely the relative movement between the loop and the magnet that produces the variation in the magnetic flux.
Question 6
(UCS 2015) Costa Rica, in 2015, came very close to generating 100% of its electrical energy from renewable energy sources, such as hydro, wind and geothermal. The law of Physics that allows the construction of generators that transform other forms of energy into electrical energy is Faraday's law, which can be best defined by the following statement:
a) every electric charge produces an electric field with a radial direction, the direction of which is independent of the sign of that charge.
b) every electric current, in a conducting wire, produces a magnetic field with a radial direction to the wire.
c) an electric charge, at rest, immersed in a magnetic field suffers a centripetal force.
d) the electromotive force induced in a loop is proportional to the rate of variation of the magnetic flux in relation to the time taken to make this variation.
e) every electromagnetic wave becomes a mechanical wave when it passes from a denser medium to a less dense one.
The induced electromotive force is the ratio between the variation in magnetic flux and the time interval. It can be expressed by the formula:
See more about Faraday's Law - Law of Induction.
See too:
- Faraday constant
- Electromagnetic Induction
- Magnetic Force: formula, rules and exercises
ASTH, Rafael. Faraday's Law exercises (electromagnetic induction).All Matter, [n.d.]. Available in: https://www.todamateria.com.br/exercicios-de-lei-de-faraday/. Access at:
See too
- Electromagnetic Induction
- Faraday's law
- Exercises on Ohm's Law with answers
- Exercises on Coulomb's Law (Electrical force)
- Exercises on the first law of thermodynamics
- Lenz's law