WE04 - Measuring Electricity

Youtube video, suitable whether of not you have the board with you.

See board images.

Tutorial guide for when you have the board with you.

Part 1

Now we are going to look at how we measure electricity, understanding this is quite amazing and make all of this electrical stuff make more sense!

The first thing we are going to look at is electrical pressure (or push). Think of water in a hose pipe, if water shots out when the tap is turned on, then it’s under high pressure, if it dribbles out then the pressure is low. Electrical pressure is measured in something called volts and every place where we get electricity from (the supply) will say how many volts it is giving us. Ensure there is no lead plugged into the board and then press the big green button. Note the meter with the V on it. This is a volt-meter and shows us the difference in the electrical pressure between two places in the circuit.

With the green button pressed, the meter is showing the pressure across the battery pack we have here. The meter should be reading about 2 and a half volts. If you look at any battery you will see the number of volts it produces written on the side of it, these have 1.2V written on them.

The second measurement is the flow of the electricity through a part of the circuit. If we think of our water pipe again it’s the amount of water coming out of the end of the hose, if it just drips out, the flow is very low, lots of water measures the flow is higher. Electrical flow (or current as we call it) is measured in amps. Meters measuring flow/current are called ammeters. Now one here, is showing there is no flow of current round the circuit.

Now plug one end of the lead into the blue socket and the other end into the socket marked D. Now press and hold the big green push switch down. The heart light should light up and the ammeter will show the amount of current flowing round the circuit. The device (here the heart light) will determine how much current flows round the circuit. Change the lead so it connects each of the four devices and note the different readings in the ammeter. The voltmeter may drop a little as the current increases, this is because either the battery is going flat (running out of power) or it’s really too small and is battery struggles to provide the amount of current required.

Part 2

Record the readings from the two meters for the four different devices on the board.

Now you can work out the total electrical power used by a device can be calculated by multiplying the number of volts by the number of amps. Power is measured in watts. The bigger the device the more watts of power it will use.

Research Brief

Find out online what voltage is used for the following:

• A USB device
• An industrial 3 phase motor
• A pylon

Some follow-up ideas to try...

• Do some research on the internet and find out the voltage used by the big pylons that make up the UK national grid.
• Find a desk or other light and identify the type of switch that is used to operate it.
• Look for the voltage on the back for some electrical devices. Some can need a specific number like 240 and they will be labelled with a V. This is the voltage supplied to our homes in the UK. Where possible products are designed to handle a range like 110-250V because other countries use different supply voltages.