Quiz 1
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Why is it important to establish an equipotential zone:
To eliminate step and touch voltage potential hazards

What are current Transformers used for? Range? Effect of opening circuit?
 For metering and protection
 05 Amps
 Opening secondary side will cause dangerous situation to allow secondary to see dangerously high voltage(don’t open)

What are potential transformers used for? Range?
 For metering and Protection
 0120 volts
 OK to open secondary

Define voltage
Voltage is the electric pressure that pushes electrons through a conductor.

Define Ohm
Resistance to current flow in a purely resistive circuit.

Define a Coulomb.
 A quantity measurement of electrons.
 1 Coulomb = 6.25 * 10^18 electrons

How can the polarity of an electromagnet be determined if the direction of current flow is known?
The left hand rule… thumb = north magnetic pole and fingers = direction of current flow.

Define Flux Density.
A measurement of magnetic strength

Define Saturation.
When a magnet eventually reaches a point where its strength increases only slightly with an increase in current.

Define Residual Magnetism.
The amount of magnetism left in a material once the magnetizing force has stopped.

State Kirchoff’s voltage law.
The algebraic sum of voltage drops and sources in a closed circuit must = 0.

State Kirchoff’s current law.
The algebraic sum of currents entering and leaving a point must = 0.

Name 3 factors that determine the amount of induced voltage in a coil.
 Number of turns of wire
 Strength of the magnetic field (flux density)
 Speed of the cutting action

Describe current/voltage relationship in a purely inductive circuit
Current lags voltage by 90 degrees

Describe current/voltage relationship in a purely capacitive circuit
Current leads voltage by 90 degrees

To what is inductive reactance proportional?
The inductance of the coil, and frequency of the line.

What is frequency?
The number of complete cycles per second.

What is the formula for calculating instantaneous voltage?
E(instant) = E(max) x sin angle theta

List 3 factors that determine capacitance of a capacitor.
 Surface area of the plates
 Distance between the plates
 Type of di electric used

Name two factors that determine the capacitive reactance of a capacitor.
Frequency and capacitance.

What is a transformer? What is the operating efficiency
 A machine which operates magnetically and changes the voltage, current and impedance without changing frequency.
 Operating Efficiency is 90%99%

What is the formula for Inductive Reactance(Xl)
Xl=2*π*f*L

What is the formula for Capacitive Reactance(Xc)
Xc=1/2*π*f*C

What is the formula for power in a 3 phase circuit
P=1.732*Eline*Iline*PF

What are 3 ways to calculate Power Factor(PF)
 PF=P/VA
 PF=cos(angle theta)
 PF=Iresistive/Itotal

What is a circuit breaker used for
To interrupt both load and fault current

What is capacitive reactance
The current limiting property of a capacitor in an AC circuit

What is inductive reactance
The current limiting property of an inductor in an AC circuit

Anytime a circuit breaker, disconnect switch or cutout is operated, one of the following six consequences occurs
 pick up load
 drop load
 energize
 deenergize
 make parallel
 break parallel

What is a ground fault
A current path to ground that was not the intended path

What range of electric current causes death? How?
 50200 milliamperes (mA)
 Through defibrillation of the heart

Define Watt
The measure of power in an electric circuit

What are 3 ways to calculate Power(single phase circuit)

Define Current
The rate of flow of electrons

Define Ohm's Law
 The electric relationship between voltage, current, resistance
 E = I * R

What is a dielectric?
A material with an electric insulating quality

Define Power Factor
Comparison of true(real) power to apparent power in an AC circuit

What is the formula for calculating impedance in a Reactor
Rx = kV / (1.732 * I rating) * Z%