ELECTRONIC CIRCUITS FOR GRADE 9

Prepared by G. C. Accom

SOME OF THE SYMBOLS WE WILL USE

SYMBOL NAME SYMBOL NAME SWITCH LDR

BULB

RESISTOR

TRANSISTOR

CAPACITOR

BUZZER DIODE

CELLS IN PARALLEL

CELLS IN SERIES

How to make a simple cell-holder for batteries

USE A PIECE OF RUBBER

HOSE AND A KNIFE

CUT A SLIT INTO THE HOSE

SLIDE THE NUMBER OF CELLS YOU NEED INTO THE SLIT YOU HAVE CUT

I GRADE 9 YOU WILL BE WORKING WITH THE FOLLOWING POWER SOURCES

EXPLAIN TO LEARNERS

WHY WE SAY THESE CELLS

ARE CONNECTED

IN SERIES

A SIMPLE CIRCUIT WITH CELLS CONNECTED IN SERIES

PUSH SWITCHALWAYS ON

SWITCH MADE WITH PAPER CLIP AND THUMB TACK

TOGGLE SWITCH

PUSH SWITCH ALWAYS OFF

PUSH SWITCH Normally ON in its normal state

It switches OFF when you press it

PUSH SWITCH Normally OFF in its normal state

It switches ON when you press it

CIRCUIT DIAGRAM FOR TWO CELLS CONNECTED IN SERIES

SWITCH OPEN

SWITCH CLOSED

CELLS CONNECTED IN PARALLELSwitch Open

CELLS CONNECTED IN PARALLELSwitch Closed

BULBS CONNECTED IN SERIES

SEE WHAT HAPPENS WHEN ONE BULB IS REMOVED

BULBS CONNECTED IN PARALLEL

SEE WHAT HAPPENS WHEN ONE BULB IS REMOVED

AND SWITCH – Both Open

AND SWITCH – One Closed

AND SWITCH – Both Closed

OR SWITCH – Both Open

OR SWITCH – Bottom switch closed

OR SWITCH – Top switch closed

OR SWITCH – Both switches closed

4,5 v battery, switch, resistor and LED

CIRCUIT DIAGRAM

LDR, buzzer, 3v battery

Buzzer sounds when light of torch is brought close

CIRCUIT DIAGRAM

LDR with LED

LED is ON in absence of LIGHT

LED is OFF in presence of LIGHT

CIRCUIT DIAGRAM

Circuit with switch, resistor, capacitor, diode & LED

NOTE- LED is OFF

NOTE- LED is ON

NOTE POWER SUPPLY IS REMOVED BUT - LED is still ON

CIRCUIT DIAGRAM

TOUCH OR MOIST DETECTORSWITCH OPEN = LED OFF

WATER

SWITCH CLOSED = LED ON

WATER

CIRCUIT DIAGRAM

YOU CAN USE EXACTLY THE SAME CIRCUIT TO ADD A BUZZER

WATER

CONNECT TERMINALS OF BUZZER HERE