# Electromagnetism

#### Chapter 15 - Electromagnetism

The last of the three fields taught in the GCE A Levels is the magnetic field. This video describes the basic properties of magnetic fields, and a simple way to model the Earth as a giant bar magnet.

For the GCE A Levels, we have to be able to visualise and draw the magnetic field pattern created by a straight current-carrying conductor using the right-hand grip rule. In addition, we need to be able to quantitatively deduce the magnitude of the magnetic flux density at any point created by a straight current-carrying conductor.

For the GCE A Levels, we have to be able to visualise and draw the magnetic field pattern created by a flat circular coil using the right-hand grip rule. In addition, we need to be able to quantitatively deduce the magnitude of the magnetic flux density at the centre of a flat circular coil.

For the GCE A Levels, we have to be able to visualise and draw the magnetic field pattern created by a solenoid using the right-hand grip rule. In addition, we need to be able to quantitatively deduce the magnitude of the magnetic flux density within the solenoid.

Current-carrying wires when placed in a region of magnetic field, can experience a magnetic force. The GCE A Levels requires us to be able to calculate the magnitude of this magnetic force, and also using Fleming’s Left-Hand Rule, deduce the direction of this force. This video will discuss these concepts.

In the GCE A Levels, we must know that two straight current carrying conductors aligned parallel to each other will exert equal but opposite magnetic forces on each other. This video will explore why this happens, and will also calculate the magnitude of the magnetic force per unit length each wire exerts on the other.

The current balance is a device that operates on the principle of moments. The GCE A Levels requires us to understand how the current balance functions, and this video aims to describe this balancing of a rectangular conducting coil, using a known mass on one end, and magnetic force on the other.

DC motors are one of the most important inventions in history. The GCE A Levels requires us to understand how DC motors work, including how the current in the coil generates a torque. The key focus of this video is to derive the expression for the torque created on the DC motor by the magnetic field and the current through the coil.

When charges move in a region of magnetic field, they can experience a magnetic force. The GCE A Levels requires us to be able to calculate the magnitude of this magnetic force, and also using Fleming’s Left-Hand Rule, deduce the direction of this force. This video will discuss these concepts.

In the GCE A Levels, we are required to analyse the motion of a charge that enters a region of uniform magnetic field, perpendicular to it. The resultant motion is a circular one as the conditions allow the magnetic force on the charge to provide a centripetal force. This video will briefly explain how this happens, and also discuss some useful derived formulae.

In the GCE A Levels, we are required to analyse the motion of a charge that enters a region of uniform magnetic field, at an angle to it. The resultant motion is a helical one as component of the velocity perpendicular to the magnetic field creates a circular motion, while the component of the velocity parallel to the magnetic field creates a constant forward motion. This video will explain these concepts.

A velocity selector is a device that only allows charged particles of a certain velocity to emerge through it un-deflected. The GCE A Levels requires us to understand how a velocity selector works, and this video will explain how it uses an electric field and magnetic field to achieve this.