Electricity in the home.

Home Electricity

•Our power points consist of two components, with an optional third•Active•Neutral•Earth (optional)

This is a typical diagram for wiring of an appliance.

Note Earth is there for safety, and not used in all appliances.

The active end is connected to the active supply and puts out an oscillating +340v to -340v or 240v RMS

The neutral end is connected to the neutral terminal of the supply box. This is then connected to the Earth, with a rod into the ground.

So the electricity flows out of the active and into the neutral.

October 2002, Norway) It's a well-known fishing trick. Put 12V electrodes into the ground if you want worms come to the surface. One 23-year-old Laagendalsposten man withdrew his genes form the pool when he tried to speed up the process. He figured that 220V, 50Hz, would bring more worms out faster, and he decided to test his theory. Alas, he did so squatting on a steel bucket, one hand holding an electrode while the other was embedded in the ground a few feet away. He seemed determined to enter the eternal fishing grounds. Quicker than spit, that wish was granted.

Darwin Award

Is this safe?

Over the next few slides, a few pictures of dangerous electricity practices, write down why it’s not good and what you could do to improve it.

Split into groups of 4 Find out about1. What kind of Voltage can kill someone?2. What effect does current have on the

human body? In respect to exposure time and/or amount of current.

3. How would you treat someone who has been shocked?

4. Name a piece of medical equipment that uses or measures electrical activity and discuss how it works.

5. Discuss with class.

The Human Body

Damaged extension cords or appliances can ‘leak’ electricity.

This leak can result in a short circuit, damaging the appliance or even you.

To stop this from happening, older buildings used fuses.

A fuse will melt if it has too much current and create an open circuit.

Fuses and Safety Features

Newer buildings and large supply boxes use circuit breakers.

If they detect a high load of current, they will open, creating an open circuit.

Circuit Breakers

Out of your power point, we run 240v AC The power is supplied at 10 Amperes

What is the power at a power point?

AC Power

Being AC, this means the direction of the flow current changes.

AC Power

Power, energy and the relationship with voltage and current.

Power is how fast energy is being converted to another form. i.e. Electricity to heat (toaster) or Electricity to sound (speaker).

Power = Energy / Time

Energy = Power x Time

As we know electricity is made up of two main parts current and voltage.

We get our Power from current and Voltage so:

Power = Voltage x Current, (P = VI)

Energy = Voltage x Current x time (E = VIt)

Most appliances have a power rating listed somewhere on them. Usually given in Watts.

A Microwave might use 12000 Watts, a Toaster 1800 Watts.

If the AC Supply is 240v and Toaster uses 1800 Watts

1. What is the current the toaster draws? 2. What is the resistance of the toaster in

use?

Power Ratings

Harry is charging his phone at home. (assume 240v rms)

It draws a current of 1.5 Amps How much power does it draw? If left charging for four hours, how much

energy has he used in;i) kWh? ii) Joules?

Storage cells are special types of cells that current can be reversed through them.

This reverses the process that produces the charge, meaning you can recharge the battery

List some common types.

Storage Cells