Fomulas

Question 1

Ohms Law 1

Answer 1

E=I R I = E/R R= E/I

Question 2

Ohms Law 2

Answer 2

P = I E E = P/I I = P/E

Question 3

Convert to dB Voltages

Answer 3

20log(#/ref)

eg—20log(50 V / 25 V) = 6dB

3dB is only a double for power changes, not voltage only

Question 4

Convert Power to dB

Answer 4

10log(#/ref)

eg

10log(50/25) = 3dB

Question 5

Voltage ratio from dB

Answer 5

10^(# / 20)

eg

5dB = 10^(5/20) = 1.77

Question 6

Power ratio from dB

Answer 6

= 10^(#/10)

eg

3dB = 10^(3/10) = 1.995 (so, 2)

Question 7

Percent voltage to dB

Answer 7

dB = 20 log (% V / 100%)

eg, a 200% voltage change:

20 log (200/100) = 6dB

Question 8

Percent power to dB

Answer 8

dB = 10log(% A / 100%)

eg, a 3000% increase in power:

10log(3000/100)=10log(30)=14.77dB

Question 9

Find percentage voltage from dB

Answer 9

100*10^(dB/20)

eg, 10dB loss (-10dB):

100*10^(-10/20)=31% voltage

Question 10

Find percent power from dB

Answer 10

100*10^(dB/10)

eg, a component loses 2dB:

100*10^(-2/10)=63% power remains

Question 11

Wavelength

Answer 11

L= c/f f = c/L

wl = 300/f f = 300/L

Use 300 bc we’re dealing with MHz, not Hz

Question 12

Peak Voltage to RMS

Answer 12

0.707*Vpk (If given peak voltage)

or

0.707*(Vp-p/2).
(If given a peak to peak voltage)

Question 13

Find Peak voltage if given Vrms

Answer 13

1.414*Vrms

Question 14

Find Vp-p

Answer 14

2.828*Vrms

Question 15

PEP

Answer 15

=(Vrms^2) / Resistance

Question 16

Transformer Voltage Calculation

Answer 16

Es/Ep = Ns/Np

Or

Es=Ep*(Ns/Np)

Question 17

Series Math

Resistor
Inductor
Capacitor

Answer 17

Add:
R1+R2+R3…
L1+L2+L3…

Reciprocal of Reciprocal
1/(1/C1+1/C2+1/C3…)

Question 18

Parallel

Resistor
Inductor
Capacitor

Answer 18

1/(1/R1+1/R2+1/R3…)
1/(1/L1+1/L2+1/L3…)
C1+C2+C3…