Basic Electronics 101
What is the formula for converting teslas to gauss?
#G = #T x (1x10⁴G/T) G = number of Gauss T = number of Tesla
What is the formula for converting webers (Wb) to maxwells (Mx)?
#Mx= #Wb x (1x10⁸Mx/1Wb)
What is the formula for converting gauss to teslas?
#T = #G x (1T/1 x 10⁴G) G = number of Gauss T = number of Tesla
What is the formula for converting maxwells (Mx) to webers (Wb)?
#Wb = #Mx x (1WB/1x10⁸Mx)
One coulomb/sec is equal to what?
1 Amp I = Q/T
1 Watt =
1 Joule/sec
What is 1 maxwell (Mx)?
1 Mx = 1 magnetic flux line
1 Joule =
1 Watt/sec
1 Amp is equal to how much charge?
1 coulomb/second
What is the typical internal resistance of a DMM?
10 M Ohms
Max Voltage for 1/8 Watt resistor
150V
1 electron volt = how many Joules
1ev = 1.6 x 10^-19 Joules
Max voltage for a 1/4 Watt resistor
250V
What is the frequency range of a typical DMM?
45 - 1000 Hz
Coulomb = how many electrons?
6.25 * 10^18
What is a circular mil?
A cmil is the cross-sectional area of a wire with a diameter of 1 mil. The number of cmils in any circular area is: cmil = d₂ (mils).
What is a node?
A common connection for two or more components.
What is a principal node?
A common connection of 3 or more components
In general a current meter should have a high or low resistance compared to the circuit being tested?
A current meter should have a low resistance As a general rule the resistance should be no higher than 1/100 of the circuit resistance
What is an important difference between voltage and current sources when analyzing circuits with Thevenin's and Norton's Theorems?
A current source is killed by making it open rather than shorting it like a voltage source.
What is considered a mesh when analyzing a circuit with the Mesh Current Method?
A mesh is the simplest closed path.
How much is a mil?
A mil is one-thousandth of an inch or .001 inch.
In Node-Voltage Analysis why do we find the voltage at a node?
A node voltage must be common to two loops.
What is a primary cell, what is a secondary cell, when referring to batteries?
A primary cell will be discarded when depleted and a secondary cell is rechargeable.
What is a Voltaic or Galvanic cell?
A voltaic or galvanic cell is an electrochemical cell that derives electrical energy from spontaneous reactions taking place within the cell
What are the requirements for Superposition?
All components must be linear and bilateral to superimpose to the applied voltage. Bilateral means that the current is the same amount for opposite polarities or the source voltage. Networks with resistors, capacitors, and air-core inductors are generally linear and passive...do not amplify or rectify Active components are typically transistors, diodes, and electron tubes and are never bilateral and often not linear
What are the three parts of a battery?
An anode (-), a cathode (+), and the electrolyte
What is an ion?
An ion is an atom or group of atoms, that has a net electric charge either positive or negative, resulting from a loss or gain of an electron.
State Norton's Theorem?
Any network can be represented by a current source and shunt resistance.
State Thevenin's Theorem
Any network can be represented by a voltage source and series resistance.
What is the formula for flux density?
B = ∅/A B = flux density ∅(phi) = flux through area A A = area
Bleeder current is roughly (rough rule of thumb) what percentage of total load current?
Bleeder current is roughly 10% of total load current.
What is bleeder current?
Bleeder current which travels through the bleeder resister. This resister is the resistor which has only bleeder current running through it, not any load current.
When dealing with wire (conductors), cross-sectional area does what for every how many wire sizes?
Cross-sectional area doubles for every 3 steps in gage. A 13 AWG wire has twice the cross-sectional area as a 16 AWG wire.
What does DIP in DIP switch stand for?
Dual in-line Package
Ohms law E =
E = IR
Why is an ohmmeter non-linear?
Equal increases in resistance does not produce equal decreases in current.
Using KVL to determine Voltages, what do you follow around the loop?
Follow electron flow direction around the loop
What are some advantages to Digital Multimeters (DMM)?
High input resistance Resistance is the same on all ranges
With any number of parallel branches, what is the formula for current, using conductance?
I = (G/Gt) x It for each branch current
What is the formula for conductance?
I = 1/R ... the inverse of resistance
Ohms Law I =
I = V/R
Currents divide inversely to the branch resistance. What are the formulas to find current in two parallel resistors?
I1 = (R2/(R1+R2)) x It I2 = (R1/(R1+R2)) x It All resistance sizes need to be in same units
State the Superposition Theorem
In a network with two or more sources, the current or voltage for any component is the algebraic sum of the effects produced by each source acting separately.
How does the method of Branch Currents differ from Node-Voltage Analysis and Method of Mesh Currents?
In the method of branch currents, currents are used for specifying the voltage drops around the loops. Then loop equations are written to satisfy KVL. Solving the loop equations, we can calculate the unknown branch currents. The Node-Voltage Analysis uses voltage drops to specify the currents at a branch point or node. Then node equations of currents are written to satisfy KCL. Solving the node equations, we can calculate the unknown node voltages. The method of node voltage analysis is often shorter. Method of Mesh Currents differs as a mesh current is assumed to flow around a mesh without dividing. Also, a mesh current is an assumed current and branch currents are actual currents.
What is a NTC Thermistor?
It's a Negative Temperature Coefficient Thermistor As temperature increases, resistance decreases
How is an Ohmmeter's ohms/volt rating calculated with Iᵐ
It's just the reciprocal of Iᵐ of the meter movement
What is the formula for finding the shunt current in an ohm meter?
Iˢ = Iᵗ - Iᵐ Iˢ = shunt current Iᵗ = total current Iᵐ = meter current
What are the three methods for analyzing complex circuits
Method of Branch Currents Node-Voltage Analysis Method of Mesh Currents
What is Millman's Theorem?
Millman's Theorem provides a shortcut for finding the common voltage across any number of parallel branches with different voltage sources.
In Node Voltage Analysis, generally, what is the number of current equations required?
One less than the number of principal nodes
What is a tesla?
One tesla = 1Wb/m² One weber per m²
Formula for Power when voltage and resistance is known.
P = (E₂)/R
Formula for Power when current and resistance is known?
P = (I₂) (R)
Power I = (With current and resistance)
P = I₂ R
P = (With voltage and resistance)
P = V₂/R
Power P = ?
P=IE
Ohms law R =
R = E/I
What is the formula for determining the resistance of wire?
R = ρ(l/A) R = resistance ρ = the specific resistance of the conductor (rho) l = length A = cross-sectional area
Special Case...How to find Req with Two Parallel branch resistors Req=
Req = (R1 x R2)/(R1 + R2)
What is the formula to find Req in a parallel circuit with 3 or more resistors?
Req = 1/(1/R1 + 1/R2 ...)
If you need to add a resistor in parallel to achieve a specific parallel resistance (Req), what is the formula.
Rx = (R x Req)/(R - Req)
In a Wheatstone Bridge what is the formula for determining the unknown resistor value?
Rx = Rs x R1/R2 Rs being the variable resistor
What is an alternate formula (quickest) for finding the shunt Resistor value in an ohm meter?
Rˢ = (Iᵐ/(Iᵗ - Iᵐ)) x rᵐ Iᵐ = meter current Iᵗ = total current rᵐ = meter resistance
What is the primary formula for determining a shunt resistor?
Rˢ = Vᵐ/Iˢ Rˢ = shunt resistance Vᵐ = voltage across the shunt resistor and meter Iˢ = current through the shunt resistor
What are the 3 formulas for converting a Y to ∆ or T to π ?
Rᵃ = (R₁R₂ + R₂R₃ + R₃R₁)/R₁ Rᵇ = (R₁R₂ + R₂R₃ + R₃R₁)/R₂ Rᶜ = (R₁R₂ + R₂R₃ + R₃R₁)/R₃
What is the formula for calculating a multiplier resistor in a volt-meter circuit?
Rᵐᵘˡᵗ = ((full scale V)/Full scale I) - rᵐ rᵐ = Meter internal resistance
What is the formula for calculating the resistance for a rise in temperature?
Rᵗ = R₀ + R₀(α∆t) R₀ is the resistance at 20°C Rᵗ is the higher resistance at the higher temp ∆t is the temperature rise about 20°C
When converting to Thevenin from Norton, what are the formulas?
Rᵗʰ = Rⁿ Vᵗʰ = Iⁿ x Rⁿ Voltage source in series with a resistor.
When converting to Norton from Thevenin, what are the formulas?
Rⁿ = Rᵗʰ Iⁿ = Vᵗʰ / Rᵗʰ Current source in parallel with a resistor.
What are the 3 formulas for converting ∆ to Y or π to T ?
R₁ = (RᵇRᶜ)/(Rᵃ + Rᵇ + Rᶜ) R₂ = (RᶜRᵃ)/(Rᵃ + Rᵇ + Rᶜ) R₃ = (RᵃRᵇ)/(Rᵃ + Rᵇ + Rᶜ)
What are the units for conductance?
Siemens (S)
When using Node-Voltage analysis where do you start each analysis loop?
Start at the common or ground node.
What is meant by the dielectric strength of an insulator?
Strength of dielectric can be thought of as the amount of voltage required to breakdown the insulator and cause it to conduct.
What is the SI?
System International - a system of units that provide a worldwide standard in the mks or SI units
What is Kirchoff's Current Law (KCL)?
The algebraic sum of the currents entering and leaving any point in a circuit must equal zero.
What is Kirchhoff's Voltage Law (KVL)?
The algebraic sum of the voltage around any closed loop is zero.
What is the cgs system?
The center-gram-second system defines small units...and in this case, it's small units of flux.
The factor α (alpha) states what concerning resistance?
The factor of α (alpha) states how much resistance changes for a change in temperature. A positive α is a rise in resistance A negative α is a fall in resistance
Define Power (non electronic formula)
The time rate of doing work...Power = Work/Time
When trouble shooting a circuit with 3 or more components what happens to voltage?
The voltage across the defective component changes in a direction that is opposite to the direction of the change in voltage across the good components.
What is loaded voltage
The voltage at a point in a series voltage divider where a parallel load has been connected
What is the unit of Gauss?
This unit is 1 line of flux per square centimeter or 1Mx/cm²
What are some of the elements used for creating a high resistance wire such as those in a toaster?
Tungsten Nickel Iron alloys such as: Manganin Nichrome Constantan
Voltage Dividers... in a series circuit what is the formula for resistance across one resistor?
V = (R/Rt) x Vt All resistances need to be in the same units
What is the formula for voltage when I and G are known?
V = I/G I = Current G = Siemens
What is the correction formula for the loading effect when a VOM does not have a high enough resistance?
V = Vᵐ + ((R₁ x R₂)/(Rᵛ (R₁ + R₂))) x Vᵐ Vᵐ = The actual reading on the meter Rᵛ = Meter internal resistance
What is Millman's formula for determining voltage across any number of parallel branches?
Vˣʸ = (V₁/R₁ + V₂/R₂ + V₃/R₃...) / (1/R₁ +1/R₂ + 1/R₃...) If a branch does not have a voltage source then its voltage is zero. This can only be used if ALL branches are in parallel with no series resistors in between branches.
What is a weber (Wb)?
Weber is a larger unit of magnetic flux measurement. 1 Wb =1 x 10⁸
What are the typical use of slow blow fuses
Within a motor circuit. Motor starting current is usually much higher than its running current.
An ideal current source is assumed to have an internal resistance of what?
infinite ohms.
What is the difference between mils and cmils?
mils is a length in inches and cmils is area. cmils will typically be x10 raised to the -6th power.
What is the symbol for flux?
phi ∅
What is the formula for measuring the internal resistance of a generator or battery with Voltage and Resistance?
rⁱ = ((Vⁿˡ- Vˡ)/Vˡ) x Rˡ rⁱ = internal resistance Vⁿˡ = no load voltage Vˡ = loaded voltage Rˡ = Resistance load
What is the formula for measuring the internal resistance of a generator or battery with voltage and current
rⁱ = (Vⁿˡ- Vˡ)/Iˡ rⁱ = Internal Resistance Vⁿˡ = Voltage no loag Vˡ = Loaded Voltage Iˡ = Loaded Current
