What are the basic electronic components, and how is Ohm's law used in a circuit?
Electronic components and quantities: conductors and insulators, resistors, capacitors, diodes and LEDs, and using Ohm's law V = I R.
A CCEA GCSE Technology and Design answer on basic electronics: conductors and insulators, resistors, capacitors, diodes and LEDs, current, voltage and resistance, and using Ohm's law V = I R including a current-limiting resistor calculation.
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What this dot point is asking
CCEA wants you to know the basic electronic components - conductors and insulators, resistors, capacitors, diodes and LEDs - the quantities current, voltage and resistance, and how to use Ohm's law, V = I R, including working out a current-limiting resistor for an LED. This is the electrical foundation of the topic.
The answer
Conductors and insulators
Current, voltage and resistance
Common components
Ohm's law
Why an LED needs a resistor
Worked example: sizing a current-limiting resistor
Examples in context
- Example 1. A wire and its insulation
- Copper conducts the current along the wire; the plastic sleeve insulates it so it is safe to touch - conductor and insulator in one component.
- Example 2. An LED indicator on a device
- A small series resistor sets the LED current from the supply, using Ohm's law, so the LED is bright but not damaged.
- Example 3. A potential divider in a sensor
- A fixed resistor and a sensor resistor share the supply voltage, and Ohm's law explains how the voltage splits - the link to input subsystems.
Being able to use Ohm's law and size an LED resistor lets you answer both the straight calculation questions and the applied resistor-design questions.
Try this
Q1. Give one example of a conductor and one example of an insulator. [2 marks]
- Cue. Conductor: copper (or any metal). Insulator: plastic, rubber or glass.
Q2. State Ohm's law. [1 mark]
- Cue. (voltage = current x resistance).
Q3. A 12 V supply drives 0.04 A through a resistor. Calculate its resistance. [2 marks]
- Cue. .
Q4. Why does an LED need a series resistor? [2 marks]
- Cue. To limit the current to a safe value; without it the LED would draw too much current and be destroyed.
Q5. What is the function of a diode? [1 mark]
- Cue. It allows current to flow in one direction only.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style3 marksA resistor has a voltage of 6 V across it and a current of 0.02 A through it. Calculate its resistance.Show worked answer →
Rearrange Ohm's law for resistance: (1).
(1).
So the resistance is 300 ohms (1).
CCEA style4 marksAn LED needs 2 V across it and 20 mA through it from a 9 V supply. Calculate the value of the series resistor needed.Show worked answer →
The resistor must drop the remaining voltage: (1).
The current is (1).
(1).
So a 350 ohm resistor (or the nearest standard value, e.g. 360 ohm) is needed to protect the LED (1).
Related dot points
- The systems approach: representing electronic and control systems as input, process and output blocks, with feedback, using block (systems) diagrams.
A CCEA GCSE Technology and Design answer on the systems approach: describing an electronic or control system as input, process and output blocks, the idea of feedback, and using block (systems) diagrams to design and analyse a system.
- Input subsystems: switches, the light-dependent resistor, the thermistor, and the voltage divider that turns a sensor's resistance change into a voltage signal.
A CCEA GCSE Technology and Design answer on input subsystems: switches, the light-dependent resistor (LDR) and the thermistor, and how a voltage divider (potential divider) turns a change in a sensor's resistance into a changing voltage signal for the process stage.
- Output devices: lamps, buzzers, motors and relays, and the transistor used as an electronic switch to control a larger current from a small input.
A CCEA GCSE Technology and Design answer on output devices: lamps, buzzers, motors and relays, and how a transistor acts as an electronic switch, turning a small input current into the switching of a much larger output current, with a protection diode for inductive loads.
- Logic gates and digital control: the AND, OR, NOT, NAND and NOR gates with truth tables, combining gates, and flowcharts for program control.
A CCEA GCSE Technology and Design answer on digital control: the AND, OR, NOT, NAND and NOR logic gates with their truth tables, combining gates to make a decision, and using flowcharts (sequence and decision) for program control.
- Microcontrollers (PICs) and timing: programmable control with a microcontroller, and resistor-capacitor timing where the capacitor charges to create a delay.
A CCEA GCSE Technology and Design answer on microcontrollers (PICs) and timing circuits: how a programmable microcontroller controls inputs and outputs, the advantages of programmable control, and how a resistor-capacitor circuit charges to create a time delay.
Sources & how we know this
- CCEA GCSE Technology and Design specification — CCEA (2017)