A


B


C


D


circuit 1 cell, 1 lamp 2 cells 1 lamp


One cell provides only 1,5 V of potential difference to the current.


Two cells in series provide 3 V of potential difference to the current.


3 cells 1 lamp


Three cells in series provide 4,5 V of potential difference to the current.


3 cells 1 lamp, steelwool


If a resistor (such as steelwool) is added in series with the lamp, the current is reduced, causing the lamp to be dimmer.


(15) Investigating Ohm’s law


In short, Ohm’s law states that the more cells connected in series, the more the strength of the current increases if the resistance does not change.


Activity 2 Test the strength of electrical current


1 Build a basic circuit with cells, wires and a lamp. Start with only one cell in your circuit.


2 Connect a second cell and a third cell in series. 3 Record what you notice about the brightness of the lamp.


(10) Investigating logic systems


Switches are the basis for all digital electronics, from cellphones to computers. Most electronic systems consist of thousands of switches. These switches can be either on or off. There are only two states. This is referred to as a binary system. Simple switches help us to understand these systems. Logic systems can become very complicated depending on how many switches are involved.


Activity 3 Investigating logic


1 Carefully read through the case study on page 152, and look at the illustrations. Make sure you understand how logic is used.


2 At the end of your investigation, write your own explanation of AND and OR logic gates, using your own examples.


(5) Practical Assessment Task 151


Did you know? The binary


system is used in every computer, cellphone, TV register or other electronic device. It is based on switches being on and off. The on switches are represented by 1s and the off switches are represented by 0s.


Did you know?


The relationship between potential difference, current and resistance is fixed. This is called Ohm’s law. Next year you will use Ohm’s law to work out values for current, potential difference and resistance.


TERM 4


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