Electronics Flashcards
Ohms law
/ V \
/ I | R\
AC current
Alternate current
Flows in different directions. Used to supply power to houses.
DC current
Direct current
Flows in one direction.
Used in batteries, household electronics
Function of a transformer
It is used to maintain a current of electricity by transferring energy between two or more circuits.
What is a voltage rectifier?
Converts AC to DC
Darlington pair
Two transistors linked together to amplify current.
Function of Capacitors and examples of where it’s used. Units
Capacitors store energy for a period of time.
They are used in camera flashes, computer emergency shut down, AC to DC conversions.
Unit: farad
Give examples of inputs, processes and outputs.
Input- LDR, thermistor, switch
Process- microchip, transistor, resistor, genie board
Outputs- led, bulb, buzzer, relay
With the aid of a diagram list the characteristics of an led.
Has two legs.
Anode-longer and positive.
Cathode-shorter and negative.
Flat edge on negative side
How to identify a resistor
4 colour bands. 1st colour- first no. 2nd colour- second no. 3rd colour-no. of 0s 4th colour-+/- 10%-silver /5%-gold
How to calculate voltage across a potential divider setup.
Voltage across R1:
R1
—— X Source Voltage
R1+R2
How to calculate resistors in parallel
1 = 1 + 1
—– —- —-
Rtotal R1 R2
Calculating Resistors in series
Rtotal =R1+R2+R3…..
Advantages and disadvantages to wiring in parallel
Adv: If one bulb breaks the rest work. All receive equal amounts of current.
Dis: Depletes battery quickly
What is a relay and examples of where used.
A relay is an electro-magnet switch that links a low power circuit to a high power circuit.
It can be used in a sensor circuit that triggers a large motor.
Forward voltage
The maximum voltage required to light an led. (Vf)
Note!!
The intensity of current flow (amps) is dependant on the voltage source. The bigger the voltage the bigger the current and vice versa.
The bigger the resistance, the bigger the voltage must be to push the current through it.
What measures the voltage, current and resistance and how is it connected to the circuit.
Voltage: Voltmeter, wired in parallel
Current: Ammeter, wired in series
Resistance: Ohmmeter
How to wire a DPDT switch.
X across at sides and battery connection in middle
Potential divider setup.
High: sensor on top, resistor on bottom
Low: sensor on bottom, resistor on top
Draw a relay circuit for detecting high water levels which switches on a motor.
Probes at top. Transistor, two resistors, diode, relay, motor
Transistor formula
Current gain= Ic/Ib
Ratio between the current going in (base) and the current going out (collector)
What is a solenoid
An electrical device that converts electrical current into movement in a straight line. Used in a relay.
Function of a Diode
Prevents excess current generated by larger circuit getting back into the sensitive sensor circuit..
Prevents back EMF (an electric kickback) being generated.
