Electromagnetic Phenomena – a magnetic field always surrounds a conductor in which an electric current is flowing Left Hand Thumb Rule – Predicts the direction of magnetic flux around a conductor - the magnetic field exists only while the current is flowing Electromagnet – A temporary magnet that consists of a solenoid and iron core (used in remote switches and locks in x-ray) - the iron core increases the strength of the magnetic flux around the wire - the strength of the electromagnet depends on: 1. the number of loops in the solenoid 2. current strength 3. permeability of the iron core

Electromagnetic Induction Michael Faraday said: When a conductor cuts across a magnetic flux or is cut by a magnetic flux, an electromotive force (EMF/potential difference/voltage) is induced in the conductor. The size of the EMF is determined by: 1) Speed – Number of lines cut per sec. 2) Strength of the magnetic field 3) Angle between the conductor and magnetic field 4) Number of turns in the conductor

In Summary: Three Ways to Induce an EMF in a Conductor 1) Move the wire (conductor) 2) Move the magnetic field across the conductor 3) Vary the strength of the magnetic field When a conductor and magnetic field move relative to each other, an EMF is induced into the conductor

Direction of the Induced Current Determined by the left hand (dynamo rule) – Shows the direction of the current based on the relationship between the motion of the conductor and magnetic field,

Self-Induction A back emf in a wire coil produced by the magnetic flux in a wire coil that tends to oppose the applied emf. - Occurs as electrons change direction in AC or at the make/break of a switch with DC - This principle is often used to control emf in x-ray devices - Inserting an iron core in the coil can increase the bucking effect of the back emf I ) -

Mutual Induction Two insulated coils setting beside each other, one supplied with AC will induce an emf in the other coil due to the fluxuating magnetic field.