Electronics 3
Act 3
Act 3
- Multimeter
- Series parallel circuits
- Circuit symbols
- Switches / Resistors
Measuring Tools
Measuring Tools
Questions
- What is a multimeter?
- How is a multimeter used to measure voltage, current?
A multimeter is a simple tool used to measure Voltage, current or Resistance. Watch the video here.
- Voltage : Tap the probe in parallel with the components you want to measure.
- Current: Connect the probe in series with the components you are measuring.
- When measuring voltage and current, multimeters are connected/ tap together with the circuits with batteries and other components.
- Multimeters can also be used to measure resistance and check if a circuit is working. ( testing for open or closed circuit)
Series and Parallel circuit. Watch the video here
Questions
- Draw and explain a simple series and parallel circuits using two bulb, a cell and switches.
- What are the difference between series and parallel circuits?
- In terms of the voltage across the bulb?
- In terms of the current flowing across the bulb?
Circuit Symbols
Circuit Symbols
Circuit symbols are used in circuit diagrams showing how a circuit is connected together. To build a circuit you need a different diagrams to show how the components are connected together.
The List of common circuit symbols are shown here. Not all are part of D&T syllabus.
Questions
Draw and label the circuit symbol of the following
- Cell
- Resistor
- LED
- Capacitor
- LDR: Light dependent resistor
- diode
- NPN Transistor
- Bulb/Lamp (indicator)
- Motor
- Buzzer
- Switches : SPDT/ SPST / DPDT /DPST / Push to break switch/ Push to make switch
- Variable resistor
- Potetiometer
Switches
Switches
- What are the different types of switches available.
- How to apply switches in Series and parallel circuit.
Common types of switches used in Electronics circuits are
- SPST: Single pole Single Throw
- SPDT: Single Pole double Throw
- DPST: Double throw Single Throw
- DPDT: Double pole double throw
Watch the first 4 minute of the video here.
Resistors
Resistors
- A Resistor is an electronic component used to control the current flowing in a circuit.
- We learned that ohms law state that V = IR. Therefore to control the flow of current in a circuit, we can either control V or R.
- We control V by varying the voltage ( adding more batteries in series)
- We control Current (I) by adding or reducing resistance. Increasing resistance by means of adding resistor in a circuit.
Types of Resistor and how to obtain their values.
Types of Resistor and how to obtain their values.
- There are two main types of resistors.
- Fixed and variable resistors.
- Fixed resistors have values that cannot be changed.
- Variable resistors are types which values are adjustable.
- Example of Variable resistors are potentiometer.
Fixed Resistor: color code
Potentiometer
Understanding Resistor values
Understanding Resistor values
- There are 2 ways to obtain the values of a fixed resistor.
- Measure with a multimeter
- Read the value from the color code on a resistor
- Watch this video on how to read the color code of resistor.
- You are not required to memorise the color code but you need to know how to read the resistor value given the color code and table)
- 1st band represent the first digit
- 2nd band represent second digit
- 3rd band represent the multiplication factor
- last band ( gold / silver) represent the tolerance level 5% or 10%
Questions:
- Whats is the value of a resistor if the color code is Brown , Black, red, gold?
Potentiometer
Potentiometer
- A potentiometer is a variable resistor . It has a turning knob and 3 terminals
- The turning know allows you to adjust the value of the resistor.
- What happens when you turn the knob of a potentiometer. What the video here.
- Connecting between terminal 1 and 3 gives the maximum resistance. Connecting between 1 to 2 or 2 to 3 provides variable resistance.