Best Topics Flashcards
What are the exterior electrons called?
Valence electrons
How do you measure amps?
Insert probes to let electricity flow through them at a certain spot on the circuit
Define:
Ohms in parallel
Ohms in series
parallel - 1/r = 1/r1 + 1/r2
Series - add them together
Calculator resistors in a parallel circuit with
4 ohms
5 ohms
20 ohms
2 Ohms
What is a voltage divider?
What value do you get with
5V battery and two 1k resistors
Resistors drop voltage
5V is our Vout
You have 2.5 mA
1k*.0025 = 2.5V
2.5Volts is our Vin
You have 5Vout 100ohm in series and then two 500k ohms resistors in parallel, how would you calculate this?
Find the parallel value of R2 and R3
NewR2 = 1/Req = 1/R2 + 1/R3
New R2 plus R1 = total res
5V/total res = total amps
R1 * total amps = voltage drop for R1
Now if we wanted to find the total amps for R2 and R3 we would just take that voltage and divide it by the resistors respectively.
The formula how I originally did it was
1/req = 1/r2 + 1/r3
req + r1 = newr
r2/newr * Vin
REMEMBER LEAST SIGNIFICANT FIGURES
In terms of amps and voltage in a series circuit, what stays the same?
Amps stay the same
amps in series are always cheerie
volts in par don’t go far!
V1 + v2 + v3
In terms of amps and voltage in a parallel circuit, what stays the same?
Volts stay the same
i1 + i2 + i3
What are the pos and neg terminals called?
Anode - pos
Cathode - neg
annie and catherine
What do you call voltage dropped across an LED Vf
Forward Voltage
What is If?
Forward Current
Current passing through a component
An LED has 20mA If so that means it wants that If to function well
Vf is the drop in voltage because that’s the voltage that the LED takes up
What is Kirchhoff’s Voltage law
Total voltage around the loop is equal to all voltage drops in same loop
Just add up all the voltage drops and you’ll see they equal zero
V - IR1 - IR2 - IR3 = 0
Determine what the voltage drop is for 2 resistors on a parallel circuit
r1 / r1 + r2
r2 / r1 + r2
What are Significant Figures?
You use these when determining how many decimal places you care to take from amps to put in an equation
Significant figures are just numbers that have meaning
2V would have 1 SF
12.4 Ohm would have 3
0.12 Would only have 2 since that one doesn’ t really mean anything
We use the least significant figure in math
so 5V / 300 ohms = .01 < we only use the one sigificant figure specified by the 5
What is energy measured in?
What does Wattage mean?
Joules
Watts = Joules/seconds
W = V * I
Also means power
What are power ratings?
How much power a component can take before something bad happens
Normally calculated in watts
How does AC flow work
When the hill is high it goes one way, low it goes the other
What is AC frequency?
How many times a wavelength hits zero (in between)
What is 40 Hz
The signal passes 0 40 times in a second
What are AC frequencies made up of
Amplitude (peak voltage) - max voltage reached by the signal, it is measured in volts (). Negative voltage just means current is going the other way.
peak-peak voltage - twice the peak voltage. (just a measurement of peak to peak)
Time Period - time taken for signal to complete one cycle. Measured in seconds. Often shorter though. Full cycle is one pos peak, one neg peak and back to zero.
Frequency - number of cycles per second, measure in hertz Hz
What are the equations for frequency and time period
frequency = 1/time period
time period = 1/frequency
What is RMS voltage?
What are the equations for peak and RMS voltage?
Root Mean Square Voltage
It is the equivalent steady DC value which gives the same effect.
It’s 0.7 of peak voltage
We use this because the voltage is not at the peak voltage constantly.
Vrms = 0.7 * Vpeak
Vpeak = 1.4*Vrms
Only true for sign waves (most common)
If you put your multimeter in an outlet, what voltage will it show?
RMS voltage
What are capacitors made of?
two metal plates and dieletric insulated material
dieletric keeps dc current from flowing between the sheets
The closer the plates are the higher the capacitance
What is it called when a little bit of current leaves a capacitor when it shouldn’t
Leakage current
What is the resistance of a capacitor called?
ESR - Equivalent series Resistance
This is the actual resistance whereas
XC (reactive resistance) is a measure of opposition to the AC current caused by the capacitors storing and releasing of energy
What is the difference between what the capcitor says it can store vs what it might actually be called?
Tolerance
How do you calculate the amount of charge a capacitor can hold
Charge (q) = C*V
capacitance * voltage
What does a farad literally measure?
1 farad is the capacitacity to store one unit of energy (coulombs) per every volt
How does a capacitor know what charge to go to?
Current rises with the voltage rising, so when the voltage is the same for a length of time, it get’s no current.
So if you have 5V and a capacitor has access to it, as the voltage rises in terms of charge the current steadily goes up, when the charge reaches the full 5v it is at a steady flow, meaning no more charge.
