1
Laboratory Exercise #6
Faraday's Law.
Hunter College
Physics 120
Professor: Guy Okoko
, 2
Faraday’s Law of Induction
Introduction
Faraday’s Law of induction, one of the 4 essential laws of classical electromagnetism,
demonstrates how magnetic fields interact with electric circuits. Named after the one who
discovered it in 1831, it essentially states that a circuit of comprising an area A which
experiences a time-varying magnetic field B produces an emf:
∆(Φ𝐵)
ℇ= − Δ𝑡
where Φ𝐵 corresponds to the magnetic flux, and is equal to:
Φ𝐵 = 𝐵 • 𝐴 • 𝑐𝑜𝑠θ
Thus, the emf can be produced by changing the magnetic field (the magnitude or direction) or
the area of the circuit. If the circuit comprises N turns of a coil, then the area A would be
replaced by N * A.
This emf induces a current in a circuit, which in turn creates its own magnetic field. But what
direction does this current flow? Simply put, the current will always flow in such a way that the
induced magnetic field opposes the original change in flux.
The principle of induction - that a changing magnetic field can produce a current - has
far-reaching applications in everyday society. Transformers use the fact that a primary coil
containing a time-varying current can induce a current in an adjacent secondary coil, allowing
for the wireless transmission of energy, as well as stepping up and down voltages from power
stations to homes. In addition, mechanically rotating a coil around a stationary magnet (or vice
versa) produces induced currents in the coil, leading to the generation of electricity.
Laboratory Exercise #6
Faraday's Law.
Hunter College
Physics 120
Professor: Guy Okoko
, 2
Faraday’s Law of Induction
Introduction
Faraday’s Law of induction, one of the 4 essential laws of classical electromagnetism,
demonstrates how magnetic fields interact with electric circuits. Named after the one who
discovered it in 1831, it essentially states that a circuit of comprising an area A which
experiences a time-varying magnetic field B produces an emf:
∆(Φ𝐵)
ℇ= − Δ𝑡
where Φ𝐵 corresponds to the magnetic flux, and is equal to:
Φ𝐵 = 𝐵 • 𝐴 • 𝑐𝑜𝑠θ
Thus, the emf can be produced by changing the magnetic field (the magnitude or direction) or
the area of the circuit. If the circuit comprises N turns of a coil, then the area A would be
replaced by N * A.
This emf induces a current in a circuit, which in turn creates its own magnetic field. But what
direction does this current flow? Simply put, the current will always flow in such a way that the
induced magnetic field opposes the original change in flux.
The principle of induction - that a changing magnetic field can produce a current - has
far-reaching applications in everyday society. Transformers use the fact that a primary coil
containing a time-varying current can induce a current in an adjacent secondary coil, allowing
for the wireless transmission of energy, as well as stepping up and down voltages from power
stations to homes. In addition, mechanically rotating a coil around a stationary magnet (or vice
versa) produces induced currents in the coil, leading to the generation of electricity.
