Topic 3-electricity and electronics Flashcards
(21 cards)
What is alternating current?
Alternating current is when the current changes direction every fraction of a second. The mains supply a.c.
In the UK, what is mains voltage and frequency?
Mains voltage:230V
Mains frequency: 50Hz
What is direct current?
Direct current is when the current passes in one direction only. Batteries supply d.c.
How can you measure the difference between a.c. and d.c.?
Connect the supplies to an oscilloscope
How do you measure peak voltage?
Count number of boxes from centre of the wave to the top then multiply by the y-gain.
How do you measure frequency of an a.c. supply?
Count the number of boxes for one complete wave then multiply by the time-base setting to get the period of the wave, then use the equation f=1/T to calculate the frequency.
What is the definition of voltage?
Voltage is the energy given to the charges in a circuit. Measured using a voltmeter
What is the definition of resistance?
Resistance is the opposition to the flow of charge in a circuit.
What is the definition of power and what is it measured in?
Power is the energy transferred each second and is measured in watts,W
What is the definition of current?
Current is the charge flowing in one second.
What does a step- up transformer do?
Increases the voltage and decreases the current.
What does a step down transformer do?
Decreases the voltage
What are the3 parts to an electronic system?
Input, process, output.
What do Input devices do?
Convert heat, light, sound or movement to electrical energy.
What does the processor do?
Changes the electrical signal in some way.
What does the output device do?
Hanged electrical energy to heat, light, sound or movement
Name 3 output devices and there energy changes
Loudspeaker: electrical to sound
LED:electrical to light
Lamp: electrical to light
What does anLED do?
Converts electrical energy into light, but will only do so when it is connected the correct way round
Name3 input devices and there energy change.
Microphone: sound to electrical
Thermocouple: heat to electrical
Solar cell: light to electrical
Name 3 input devices that are resistance changers and state what the resistance depends on.
LDR- resistance depends on light level
Thermistor- resistance depends on temperature
Variable resistor- resistance depends on the length of resistance wire
What are the2 types of transistors?
N- channel enhancement MOSFET and NPN transistor
