Electrical safety

Here we introduce the risks and safety measures associated with the use of electricity.  The risks (fibrillation, burning, electrocution, fire etc) are managed with a range of common methods including fuses, circuit breakers, earth leakage devices, double insulation and earthing.  The effect of different sized current flows on the human body is also outlined.

Powerpoint slides

Magnetism

These slides recap some ideas from junior science (north and south poles, magnetic fields, representing magnetic fields), and the right hand grip rule is introduced (used to determine direction of magnetic field around a current carrying conductor).  Conventions for representing field lines in/out of the page are also explained (and current in/out of the page).  The magnetic field created by a solenoid (electromagnet) is also described.

Powerpoint slides

Power

Most electrical quantities (resistance, voltage etc) are not immediately useful to consumers.  Electrical power on the other hand, is very useful, and is often mentioned during appliance retail (eg. this is a 200W stereo system).  Power (and electrical power) is a measurement of how many joules of energy can be changed from one form of energy to another form.  It is measured in joules per second (or, equivalently, watts).

These slides introduce the concepts of power, electrical power, the kilowatt-hour, and provide some calculations.

Powerpoint slides

Resistance

Resistance is an important concept in electrical theory.  Simply put, resistance is the opposition to electric current.  Insulators have a high resistance, conductors have a low resistance.  Whenever a current flows through something with resistance, it loses energy (resulting in a voltage drop).

These slides outline the concept of electrical resistance, Ohm’s Law, resistors in series, resistors in parallel, and factors which effect resistance (type of material, length, cross sectional area and temperature).

Powerpoint slides

Resistors on a circuit board