Chapter 29: Faraday's Law

Moving charges create a magnetic field (think of current in a wire).  Do changing magnetic fields create an electric field?  The answer is yes and Faraday's law describes exactly what happens.  A changing magnetic field induces a current in a conductor.  Similarly, if a conductor moves in and out of the field, the same effect and is described by Faraday's law: a changing magnetic flux (magnetic field times cross-sectional area) induces an emf (a voltage) which causes a current in a closed loop.  Lenz's law (which is part of Faraday's law) tells you that the induced current flows in a direction to oppose the change in flux.

Table of Contents

Illustrations

• Illustration 29.1: Varying Field and Varying Area.
• Illustration 29.2: Loop in a Changing Magnetic Field.
• Illustration 29.3: Electric Generator.

Explorations

• Exploration 29.1: Lenz's Law.
• Exploration 29.2: Force on a Moving Wire in a Uniform Field.
• Exploration 29.3: Loop Near a Wire.
• Exploration 29.4: Loop in a Time-Varying Magnetic Field.
• Exploration 29.5: Self-Inductance.

Problems

• Problem 29.1: Find direction of current.
• Problem 29.2: Graph current versus time.
• Problem 29.3: Find the force on a loop.
• Problem 29.4: Rank currents in a loop.
• Problem 29.5: Find emf in loop in changing magnetic field.
• Problem 29.6: In which direction is current flowing?
• Problem 29.7: Bar magnet inserted through a loop.
• Problem 29.8: Determine the direction of the magnetic field through the loop.
• Problem 29.9: Find the magnetic field.
• Problem 29.10: Find the field in a generator.
• Problem 29.11: Find the inductance of a solenoid.