Embedded Files
Lenz’s law is a manifestation of the conservation of energy. The induced emf produces a current that opposes the change in flux, because a change in flux means a change in energy. Energy can enter or leave, but not instantaneously. Lenz’s law is a consequence. As the change begins, the law says induction opposes and, thus, slows the change. In fact, if the induced emf were in the same direction as the change in flux, there would be a positive feedback that would give us free energy from no apparent source—conservation of energy would be violated. - OpenStax
As the loop begins to move into the magnetic field, the magnetic flux through the loop is increasing and so an emf (voltage) will be induced in the loop.
F = Force Electric [N]
V = Voltage / emf [J/C]
E = Electric Field [N/C]
q / e = charge / electron [C]
v = velocity [m/s]
B = Magnetic field [T]
Δx / L = Length [m]
An electric field can be described as:
Where V is the potential difference or emf and the change in x is the Length of conductor within the magnetic field.
Recalling that:
Show that:
Deriving vBL
Deriving vBL
Suppose a wire of length L is moving through a constant magnetic field (B) at a velocity of v. Show that the induced emf is equal to vBL.
This can be reordered to show emf = vBL.
Power Dissipated thru Loop.
Power Dissipated thru Loop.
Recall:
According to Lenz's Law the direction of the current is counter-clockwise (looked at from above). When the leading edge of the loop enters the magnetic field (B), a force is acting on the length (L), inducing a current (I).
From 5.4 - F = BIL sinθ, θ=90˚
From 2.3: Work, Energy and Power:
In order to push this coil into the magnetic field, a force must be applied through a distance (Work) to counteract the Lenz's current.
The rate at which the coil is moved into the the magnetic field is velocity (v).
Therefore, energy is conserved while moving the coil into the magnetic field.
Page updated
Google Sites
Report abuse