Electric Circuits Continued

In previous lessons, we learnt about current, voltage and resistance. In the next set of lessons, we will learn about Ohm's law and power and energy. We will see how to apply the concepts learnt in a previous lesson and series and parallel circuits to more complex circuit problems. The following list provides a summary of the concepts covered in the next set of lessons.

Ohm's law

In previous lessons, we learnt about parallel and series circuits, as well as the concepts of voltage, current and resistance. These concepts are now brought together in Ohm's law. Ohm's law relates voltage, current and resistance. Ohm's law only applies to Ohmic resistors (such as most resistors) and does not apply to non Ohmic resistors (such as light bulbs). Ohm's law is introduced and then we get to see it in action in various circuits.

The first circuits covered are simple series or simple parallel circuits. Once we are comfortable handling calculations for these circuits, series and parallel networks are introduced. In these circuits, we need to carefully work our way through the circuit calculating the equivalent resistances for each separate part of the circuit.

Electrical power

The concept of electrical power is introduced. A source of energy is required to drive current round a complete circuit. This is provided by batteries in the circuits you have been looking at. The batteries convert chemical potential energy into electrical energy. The energy is used to do work on the electrons in the circuit.

Power is a measure of how rapidly work is done. Power is the rate at which the work is done, work done per unit time. Work is measured in joules (J) and time in seconds (s) so power will be \(\frac{\text{\text{J}}}{\text{s}}\) which we call a watt (W).

Electrical energy

The final part of this section deals with electrical energy. This has real world applications in teaching you about how much electricity various appliances use around your home. You are encouraged to make a list of as many appliances as possible that you use and find the power rating for the appliance. This is usually given on the back of the appliances. This part of the section helps us understand some of the power saving tips that we are always told and helps to rationalise these tips. For example, we can calculate how much it costs to leave a \(\text{100}\) \(\text{W}\) bulb burning all night compared to leaving it on for just an hour.

The study of electrical circuits is essential to understand the technology that uses electricity in the real-world. We depend on electricity and electrical appliances to make many things possible in our daily lives. This becomes very clear when there is a power failure and we can't use the kettle to boil water for tea or coffee, can't use the stove or oven to cook dinner, can't charge our cellphone batteries, watch TV, or use electric lights.