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What are the formulas described by ohms laws?
- EMF( V)= Current (I)× resistance(R)
What do Weber's and Maxwell's measure, and how Do you convert one to the other?
- The overall magnetude or quantity of a magnetic field.
- Weber's(WB)=1 V•s=108 Maxwell's (Mx).
- Mx=10-8 Wb
What do Tesla's and Gauss measure and how do they compare?
- The concentration, or intensity of the magnetic field as its flux lines pass at right angles through regions having specific cross-sectional areas.
- 1 Tesla (T)=10,000 Gauss (G)
What do amper turns (Ar) and Gilbert's (Gb) measure? How do we convert Amper turns to Gilbert's and vice versa?
- They measure magnetomotive force inside a coil. (1 amp of Í through 1 loop or coil = 1 At)
- At×. 1.257=Gb
- Gb× .7598=At.
How is flux density(B) calculated at a certain point at a distance (r) from a wire carrying a current (I)?
How do you calculate flux density inside a solenoid (wirecoil)?
- Bt=4Π×10-7 ynI/s. =1.2566×10-6ynI/s
- Bg=4Π×10-3 ynI/s =.012566 unI/s
- Bt=magnetic density in Tesla's
- Bg=magnetic density in Gauss
- n=coils total turns
- I=current in amps
- s=total length of coil in meters.
In a pure sin wave where peak positive and peak negative are equal, how do you calculate root mean square amplitude?
RMS=.707 times the positive peak, or -.707 times the negative peak value.
How many charge carriers are in 1 Coulomb?
What are the formulas to calculate power in watts when only two of three variables are known(V,I,R)?
What units measure energy, and how do they compare?
- 1 joule (J)=
- 1 Watt second(Ws)=
- .000278 Watt hours(Wh)= 10,000,000 erg=
- .000948 btu's=
- 6.2×1018 eV=
- .738 ft-lb.
What is it called when diodes are used to change both positive and negative polarities on an AC circuit to DC?
Full wave rectification.
What are all the uses of resistor ?
- Voltage division
- Current limiting
- Power dissipation
- Bleeding off charge
- Impedance matching.
What is the formula for potential difference acrossed a resistor in a voltage divider?
How do you calculate decibel (dB) change based on supply power change?
- dB=10 log (Q/P)
- Q=Watts after change.
- P=Watts before change.
What are the basic manufacturing rates of resistors? Multiplied by powers of 10
What are precision manufacturing rates for resistors in 10 multiple.?
What is an inductor and the units of inductance (L)?
- Inductors oppose the flow AC by storing energy as a magnetic field.
- The unit of inductance is the Henry.
- 1 Henry = a potential difference of 1 volt accross an inductor which current increases at 1 Amp per sec.
What is the coefficient of coupling? (k)
The quantified extent to which two inductors interact (on a scale of 0 to 1)
How is mutual inductance (M) calculated?
How is reinforced mutual inductance measured for inductors in series?
How is opposing mutual inductance measured for inductors in series?
What is equal to 1cycle per second (cps) ?
What is the reciprocal of a Hertz?
A period, which shows the time it takes for 1 cycle to end and another to begin.
What are the two most common transmission line configuration?
What is the definition of capacitance?
The ability of 2 plates and the space between them to store electrical energy.
What factors determine how much voltage a capacitor can handle?
- The thickness of the plates
- The space between them
- And the type of the dielectric used.
What is a farad?
The standard unit of capacitance shown as a ratio between the current that flows, and the rate of voltage change between the plates as they charge up.
1F= a flow of 1A as the voltage changes at a rate of 1V/s.
How is capacity in series calculated?
The same as resistance in parallel.
What does the curved line on a symbol for a capacitor represent?
The side to be connected to a common ground point ( a point with a reference voltage of zero).
How does capacitors in parallel add up?
Like resistance in series
What are all the types of fixed capacitors?
Paper ,Mica, Ceramic, Plastic film Electrolytic, Transmission line, Semiconductor based.
What are the types of variable capacitors?
Air variable, Trimmer, Coaxial.
In an AC circuit, what is meant by saying a component has reactance?
A component that stores or releases energy.
What 2 factors are combined to form a component's impedence in an AC circuit?
Reactants and resistance.
What is the symbol of reactants and the symbol for inductive reactance?
What is the formula to calculate inductive reactance?
How do you calculate phase angle using inductive reactance and resistance? And what does that tell you about an RL circuit?
- Arctan XL/R.
- The angle demonstrates how much current lags behind voltage.
What are 2 types of reactants?
Inductance and capacitive
What is it called when a dielectric cannot provide electrical separation between the plates causing sparks or arcing?
How is reactance ,both capacitive and inductive measured?
How is capacitive reactance different from inductive reactance?
- • capacitive reactance veries inversely to frequency
- • Capacitive reactance always has a negative ohmic value.
- • in an R Xc. Circuit voltage lags current (or I leads V)
What is the formula for capacitive reactance?
True or false reactance applies to both DC and AC circuit?
False, reactance applies to AC circuits only.
How do you calculate phase angle in a R-Xc circuit and what does that tell you about the circuit.
- It tells you how much current leads. voltage.
What is Gustav Kirchhoff's first law?
Current going into any point is equal to that of the current exiting that point.
What is Gustav Kirchhoff's second law?
The sum of all volteges as you go around any DC Circuit from some fixed point, and return there from the opposite direction, and taking polarity into account, always equals 0.
What is the inverse of resistance?
Conductance (G), measured in Siemens (s).
What is the reciprocal of reactants (X) ?
How does inductive and and capacitive reactance differ from inductive and capacitive susceptance?
Inductive susceptance is negative imaginary and capacitive susceptance is positive imaginary. Just the opposite for reactance.
What is the formula for capacitive susceptance and inductive susceptance?
- Bc= 6.2832fC
- Bl =-1/6.2832fL
What 2 things are combined to form admittance?
Real number conductance and imaginary number susceptance.
- Y=G+jB. When the susceptance. Is positive.(capacitive)
- Y=G-jB when the susceptance is negative ( Inductive ).
What is the formula for absolute value of impendence in an RLC series and parallel circuit?
- Series Z=(R²+X²)^½
- Parallel Z=[R² X²/(R²+X²)]^½
How do you summarize the relationship among True Power(Pt) apparent power(Pva) and imaginary power (Px) ?
What is another name for an RF transmission line?
What kind of transmission line is used for microwave and ultra high frequency line?
What is the formula for complex impedences in series?
- Note: Resistance and reactants components add separately.
What is the formula for complex admittance in a parallel circuit?
- Note: In both impedance and admittance, the resistor could be considered part of the coil, when adding two complex numbers together.
What are the steps to calculating complex impedence in a parallel circuit?
- ♠Calculate the conductance G of the resistor
- ♠ calculate susceptance Bl of the inductor
- ♠ calculate the susceptance Bc of the capacitor
- ♠ determine the net susceptance
- ♠ Determine the quantity G²+B²
- ♠Compute R in terms of G and B using the appropriate formula
- ♠ Write down the complex impedance as the sum R+jX.
What is a power factor?
- The ratio between true power(Pt) and VA power (Pva) (apparent power or Volt-amp)
- The ratio falls between 0&1 And can be represented as a percentage.
What are the 2 ways to determine the power factor (PF) an a AC circuit
- * Find the cosine of the phase angle
- * Calculate the ratio of the resistance to the absolute value impedance.
What is a phase angle in an AC circuit?
The extent expressed in degrees ,to which the current and voltage differ in phase.
What do we say about an AC circuit that contains capacitive and inductive reactance that cancel each other out?
The circuit has resonance.
In an LC circuit involving transmission lines and antennas Resonance occurs at many frequencies. What is the name of the lowest frequency at which resonance occurs?
- Fundamental resonance frequency.
What is it callled when, in a series RLC circuit, capacitive reactants and inductive reactance cancel each other out and appear as pure resistance showing 0 resistance if there is no actual resistor in the series.
What is the condition of parallel resonance?
When a parallel RLC (GLC) circuit contains a capacitor and inductor which cancel each other out showing infinite resistance at particular frequency
What is the formula for calculating? resonance frequency
If the resistor value in an RLC series circuit decreases or the conductor value of an RLC parallel circuit decreases what happens to the fundamental residence? frequency?
It becomes more sharp or clear, And more Broad if the reversed observed.
What is a standing wave?
The non moving wave @like pattern shown when we graph current and voltage loops and nodes along a miss matched transmission line as a function of the position on the line.
In a transformer what is the name of the first coil in which current is deliberately driven through?
The primary winding.
In a transformer, what is the optimum primary to secondary coupling ratio?
E pri/E sec=T pri/T sec.
What is an eddy current?
The current loops which are induced on a coil's core and serves no purpose other than to waste energy.
How are eddy currents choked off?
By making a core of alternating thin sheets of metal and insulation.
What is histerisis and what core material is is known to have the highest?
- •Tendency for a core material to act sluggish in accepting a fluctuating magnetic field.
- • laminated cores.
What are the 2 methods for winding wire on an E core?
- shell method. we're both wires are wound on the same bar.
- Core wound, where wires are wound around opposite sides of the E core.
What formula can we use to determine primary and secondary turn ratio or voltage when impedances is a purely resistive?
Z pri/ Z sec= (T pri/ T sec )² = ( E pri/E sec)²
Whats the name of a transformer design to work over a wide range of frequencies?