S1 Bright Sparks Summary Notes

Transcription

1 S1 Bright Sparks Summary Notes Electronics Electronic systems 1 We are learning about the different parts of electronic systems. In our modern world we use electronic systems many times a day. In fact, we could say that society is very much dependent on them to make their lives easier or better in some way. There are many obvious electronic devices like: Some electronic devices aren t so obvious:

2 All electronic systems require: Input Process Output Power Here are some examples of everyday electronic systems to help your understanding. Note that there normally is no need to show the power supply in these diagrams although it is there.

3 Electronics Little Bits 2 We are learning to use the Little Bits electronic components Each Little Bit component is colour coded so that you can easily tell if it is an input device or output device etc. Given a list of components, like the one shown below, you should be able to select which components would be used to create an electronic system used for a specific purpose.

4 Here are some examples to aid your understanding: Example 1 An electronic system that sounds an alarm when a button is pressed. (i.e. panic button) Firstly we need to power the alarm Obviously we need a button Finally we need a device that makes a noise when the button is pressed Instead of drawing all these components we can simply write the name of the components in boxes as shown below: Power Button Buzzer Example 2 An electronic system that turns on a fan when it gets too hot Power Temperature Sensor Fan Example 3 An electronic system that turns on an LED and sounds a warning when it gets dark. Power Light Sensor LED Buzzer

5 Electricity Van de Graaff Generator and Circuit Symbols 3 We are investigating the purpose of a Van de Graaff Generator. 4 We are considering circuit symbols for various components. All objects in the universe, living and non-living are made up of atoms. All atoms consist of a small nucleus in the centre that contains protons and neutrons. Protons have an electrically positive charge whilst neutrons are neutral (i.e. they have no electrical charge) Orbiting the nucleus are small fundamental particles called electrons which have an electrically negative charge. Protons and neutrons are firmly fixed in the nucleus but electrons can be free to move. This is what electricity is all about the movement of electrons.

6 How it works: As the rubber belt turns, it rubs against a piece of metal connected to the dome. Electrons from the atoms that make up the rubber belt are released and build up on the dome. If you are touching the dome the electrons will move onto you. Electrons are negatively charged so they repel each other. This means that all the electrons in your hair are trying to move away from each other and as your hair is very light it stands up. If you touch someone whilst on the Van de Graaff generator the electrons on you can jump to the other person. You both feel a shock and you may see a small spark. This flow of electrons is called an electrical current. The insulation under you and the Van de Graaff generator is there to stop the electrons escaping.

7 Circuit Symbols Switch Lamp Wire/Lead Buzzer Battery Remember that we use circuit symbols because they are much easier and quicker to draw than pictures (like those in the right hand column of the table above).

8 Electricity Current in a series circuit 5 We are learning to investigate the flow of current at different points in a series circuit. A series circuit is where all the components are connected one after the other in line. The circuit below shows two lamps in series with each other. The size of the current can be measured using a meter called an ammeter. A The unit of electrical current is an ampere (A). Ammeters must be placed in series with other components in a circuit as shown below. A 3 A 1 The current in a series circuit is the same at all points. i.e. in the circuit shown A 1, A 2 and A 3 are all equal. A V 1.5 V Example:- In the circuit opposite we can see that the ammeter readings of I 1 and I 2 are equal to the supply current I s. i.e. I s = I 1 = I 2 3A = 3A = 3A

9 Electricity Voltage in a series circuit 6 We are learning to investigate what happens to the voltage in a series circuit. The electrical push which the battery gives to the charges is called the voltage. The voltage is measured in volts on a voltmeter V Voltmeters are connected across the part of the circuit where the voltage has to be measured. i.e. they are connected in parallel into the circuit as shown below. In a series circuit the total voltage measured across its components adds up to the supply voltage. i.e. In the circuit below V 3 = V 1 + V 2 V 3 Example:- V 2 V 1 In the circuit opposite we can see that the voltmeter readings of V 1, V 2 and V 3 add up to the supply voltage V s. i.e. V s = V 1 + V 2 + V 3 = = 12V

10 Electricity Current in a parallel circuit 7 We are learning to investigate the flow of current at different points in a parallel circuit. A parallel circuit is where components are connected across each other. In the circuit below two lamps are connected in parallel. For the parallel circuit below, the current in A 1 and A 4 will both be the same value. The currents in A 2 and A 3 add up to equal both A 1 and A 4. Example:- In the circuit opposite we can see that the ammeter readings of I 1, I 2 and I 3 add up to the supply current I s. i.e. I s = I 1 + I 2 + I 3 = = 18A

11 Electricity Voltage in a parallel circuit 8 We are learning to investigate what happens to the voltage in a parallel circuit. In a parallel circuit the voltage measured by the voltmeters across each branch of the circuit will be exactly the same and equal to the supply voltage. i.e. V 1 = V 2 = V 3 Example:- In this circuit we can see that the voltage across each lamp in parallel is the same and equal to the supply voltage from the battery. i.e. V s = V 1 = V 2 = V 3 12V = 12V = 12V = 12V