Electromagnetism and Optics: Principles and Applications

Henry's Experiment

If a driver or wire moves perpendicular to a magnetic field, it causes a potential difference across the ends of the conductor. This potential difference causes a current if the driver is part of a closed circuit.

Faraday's Law

Any change in magnetic flux through a circuit causes an induced current. This is produced by a known electromotive force (induced EMF), which exists only for the duration of this change in flux and is proportional to the rate of change of flow.

Lenz's Law

The direction of the induced current is such that it opposes the cause that produces it.

Alternator

An alternator consists of a flat coil of N turns, rotating with constant angular velocity within a uniform magnetic field B. In the coil, an EMF is induced to periodically vary the flow through it. This flux variation is caused by varying the orientation of the magnetic field coil, for example.

Self-Induction

Consider a circuit formed by a solenoid, a variable resistor, and a battery. The intensity that runs through the circuit is modified by moving the cursor over the variable resistor. The variable intensity in the solenoid generates a changing magnetic field, which produces a changing magnetic flux through it. The change in flow causes the onset of an electromotive force-induced current.

Transformers

Transformers are devices used to convert alternating current intensity (I) and voltage (V AC) into another current of varying intensity and high voltage, maintaining the power.

Real and Virtual Images

• Real images are formed by the intersection of the rays that converge or emerge after traversing an optical system. They are not seen with the naked eye and can be collected on a screen.
• Virtual images are formed by the intersection of the extensions of the rays that diverge at the output of an optical system. They do not really exist and therefore cannot be collected on a screen.

Focal Points and Focal Length

• F' (Image Focus): The image focus is a point on the axis such that the rays from a point at infinity, arriving parallel to the axis, are refracted so that they or their prolongations pass through F'. The distance between the image focus and the optical center is called the focal length, f'.
• F (Object Focus): The object focus is such that all rays emanating from it, or whose processes pass through it, leave the optical system parallel to the optical axis. The distance between this focus and the apex of the diopter is called the object focal length, f.