14. Match the components 1–7 with the correct symbol A–G. COMPONENT SYMBOL 1. LED
A. 2. Thermistor 3. LDR 4. Diode 5. Buzzer 6. Battery 7. Bulb K U B. C. D. E. F. G. 1. =____ 2. =____ 3. =____ 4. =____ 5. =____ 6. =____ 7. =____
Knowledge and Understanding 1. What happens to the resistance of a light
dependent resistor (LDR) when light is shone on it?
2. Draw a simple diagram for a circuit where a light turns on when a certain temperature is reached.
3. In which circuit shown on the right, A or B, will the bulb light up?
A 4. Look at the LED in the picture. Which leg, of the LED is the positive leg, A or B? T I B
A B
Thinking and Investigating 1. Design and draw a circuit that will set a buzzer off when a certain temperature is reached. 2. When the fridge is opened a light turns on. Design a circuit using an LDR that can be placed in the fridge which will warn a parent that their teenager is raiding it again.
3. How do diodes work? 4. Draw a circuit diagram for a circuit containing three LEDs in parallel. 5. LEDs are increasingly being used in place of light bulbs and in other light imaging devices such as television screens. Find out (a) where LEDs are used, (b) what the advantages of using LEDs are and (c) if there are any disadvantages to using LEDs.
