Electricity and Magnetism Electromagnetism

What is magnetism? How can you define magnetism? What is a “magnet”? The phenomenon caused by magnets What is a “magnet”? An object which can attract other objects containing iron, cobalt or nickel Types of magnets Electromagnets Permanent magnets

Magnet basics Two poles to each magnet As with electricity: North and South As with electricity: Opposite poles attract Like poles repel This is due to how the magnetic field looks Note Breaking a magnet makes smaller magnets with a N and S pole

Breaking a magnet

A Magnetic Field

Electromagnetism Magnetism caused by electricity In a coil (solenoid) or a wire How are we to know how the magnetic field (MF) will look like? Where can we find the North and South poles? Right hand rule (RHR) Wrap your hand around the wire or coil with your thumb pointing with the direction of current Fingers illustrate the flow of the magnetic field

Right Hand Rule

Right Hand Rule

Right Hand Rule

Right Hand Rule

In a Solenoid or a Wire The magnetic field can be turned on or off This is not true in a permanent magnet The direction of the magnetic field can be reversed Reversing the current reverses the field The intensity of the magnetic field can be modified A stronger current causes the magnetic field to increase

What is an electromagnet? By taking an solenoid and inserting a ferromagnetic core and turning on the current In this case, the magnetic field is coming from both the wire and the core. The field strength can be altered What can be modified to change the strength of the field?

Electromagnets

Electromagnets

Electromagnet

How to increase a MF in an electromagnet? By increasing the number of turns in the solenoid More turns = stronger field Increasing the current Stronger current, stronger magnetic field Changing the core A core with a lower magnetic remanence

Wire vs Magnet How do the magnetic fields differ? Magnet Wire Flows from North to South around the magnet Wire Flows circularly around the magnet There is no N or S