MCQs electrical circuits

DC

Kind of voltage that is produced by friction, chemical action and heat

AC

Kind of voltage is produced by a crystal

A single pip (Single vertical line spike)

On the spectrum analyzer appear AC signal having just one frequency component would look like

120kV - 500kV

At what budget do you think our might be carried between the mountains and the cities?

120-140V

At what voltages do you think power might be carried along city block to homes?

Peak value divide by square root of 2

Formula order converting value of AC to DC, if it’s also the RMS formula

Peak voltage times 2/pi

Average voltage

Form factor

RMS value divided by the average value

Rise time

It is the time required for the fall to go from 10% of its full amplitude to 90% of its full amplitude

Fall time

It is the time required for the balance to go from 90% of its full amplitude to 10% of its full amplitude

pulse width

it is the time between the point on the rising edge where the value is 50% of it full to the point in the falling edge where the value is 50% of its full amplitude

Duty cycle

It is the ratio of the pulse width to the period

Bandwidth

It is defined as the range of frequencies for which the current is equal to or greater than 70.7% of its resonant value

Series resonance circuit

It is also called as an acceptor circuit or a series trap

A series resonant circuit has this since the reactance cancel each other out and there is maximum current

Minimum impedance

63%

During the time interval equal to one time constant in a series RL a circuit, the current will change approximately

Attenuation

The reduction of an unwanted frequency of frequencies by a filter is called

Cotton and rubber

These are materials which make good insulators for power frequencies, but not for high radio frequencies

Current limiting resistors

A transistor can be protected from needless overheating by

Bleeder resistor

It is connected across the capacitor in a high voltage power supply, which safely discharge the star charge when it is off

Carbon composition resistors

Resistors that have essentially no capacitance or inductance

Metal film resistor

Type of resistor that does not have much inductance

Arcing/sparking

What effect causes switch or relay contacts to develop pits and mounds on them

high

What relative frequency circuit would require choke coils with air cores? since if an iron or ferromagnetic core in chokes would be used it will suffer losses due to hysteresis at high frequencies compared to air course, which will have no loss and is efficient at RF frequencies

Low

What relative frequency circuit would require choke coils With iron cores

Voltage induced is equal to the mutual inductance times the change in current over the change in time

This is the formula for mutual inductance given average current and inductive voltage

Decreases because the brass slug has a permeability of less than one which is less than the ideal air core. permeability equal to 1. This is also due to it being a non-magnetic alloy and being a diamagnetic. Also, it is remembered that the induction is proportional to the permeability of the material.

What happens to the inductance value of a brass slug if it is moved to the core area of a coil?

Increase the inductance

With permeability tuning, moving the core further into a solenoidal coil:

The magnetic flux in a toroidal is practically all within the core

A significant advantage in some situations of a toroidal coil over a solenoid is

Large inductance in small volume

Major feature of a pot-core winding is

Toroidal

Add a frequency of 400 Hz the most likely form for an inductor would be

Air-core

Add a frequency of 95.7 MHz the best form for an inductor would be

Increased inductance. Since it’s permeability is greater than one and the inductance is directly peopoertional to the permeability

What happens to the inductance value if a ferrite slug is moved to the core area of a coil

A time line is crossed

At what point in a sine wave is the rate of change at maximum

at peaks

At what points in a sine wave is the rate of change at zero

Eddy currents

What is decreased by laminating transformer cores?

Eddy current

are loops of electric current that are induced within a conductor when it is exposed to a changing magnetic field. Essentially, as the magnetic field changes—like when it passes through or near a metal—they induce circulating currents in the conductor. These currents create their own magnetic fields that oppose the original change (that’s Lenz’s Law). As a result, eddy currents can cause energy losses in the form of heat, and they’re used in things like induction heating, braking systems, and sometimes they reduce efficiency in transformers or motors.

Hysteresis

This is the term that indicates the inability of a core material to reverse magnetic polarity completely

Power

What really show in any transformer is always about one is the one (1:1)

Number of turns of the primary divided by the number of turns of the secondary

Transformer formula or ratio in terms of number of turns

Voltage the primary winding divided by the voltage in the secondary winding

Transformer formula in terms of voltages

Step down

A voltage step up transformer is considered a current —— transformer

Power in the secondary winding divided by the power in the primary winding

Power in the primary winding is equal to power in the secondary winding plus the power in the tertiary winding

Pp = Ps + Pt

Computing for primary secondary Or tertiary windings

Autotransformer

If a choke coil has a tap near its center, what type of transform might be?

Destroy core

What might occur if a 110 V DC is connected across a 120 V primary power transformer

Copper loss

What difficulties occur if the AC frequency fed to the transformer is too low

Air

What type of core is usually used with an RF transformer?

Iron

What type of core is usually used with an AF transformer?

When limiting resistance is in series with primary

Under what condition is DC applied safely to the primary of a transformer?

Condenser

Old term of a capacitor

High efficiency, capability to handle high voltages and low loss

Characteristics of mica capacitors

33uF

Disk ceramic capacitor might have a value of

0.01uF

Paper capacitor might have a value of

1uF - 100uF

Air-variable capacitor might have a range of

0.0254

Inches to meters

Dielectric constant

Another name for specific inductive capacity

Leakage, hysteresis, absorption

Types of loss in a solid dielectric type capacitor

Vacuum

Greatest dialect strength

Number of electrons is equal to the charge divided by the charge of an electron

N = Q/e

Formula for calculating the number of electrons that will pass through

Polarized, DC only, dry out

These are the disadvantages of electrolyte capacitors

Aluminum oxide

This is the material of the dielectric in an electrolyte capacitor

Tantalum oxide

This is the dielectric material of an improved type of electrolyte capacitor

Air, vacuum, mica

These are the materials of the dielectrics in an adjustable and variable capacitors

To equalize voltage across the capacitor

Why are resistors usually connected across capacitors in series?

45°

What is the phase relation between voltage and current in an equally resistive and capacitive reactive circuit

Positive plate

On which plate of an electrolytic capacitor does the dielectric Form

Connected with incorrect polarity, used on AC, exceeding working voltage

Which causes the exploding of electrolytic capacitors

Change in capacitance, electrolytic, dry out, may explode

Why should capacitors be kept away from Hot resistors or tubes

Power factor

Ratio of true to apparent power, cosine value of an ac circuit

Leads the current

What is the face relation of the voltage in a circuit having a lagging PF?

Power is equal to voltage times current times the power factor

P = VIPF

Formula for finding the voltage, current, or power given the power factor

Effective reactance is equal to the inductive reactance minus the capacitive reactance

Xeff = XL - Xc

This is the formula for finding the effective reactance

Real or active power in what is equal to

Reactive power is equal to

Apparent power is equal to

Apparent power is greater than the real or active power

S > P

Four circuits with inductive or capacity loads, which power is higher

Formula for calculating the phase angle in a reactive circuit

10 times

In most practical applications, how much greater should the X value be than the R to allow R to be disregarded?

G - conductance

Letter that symbolizes or Represents 1/R; Reciprocal of resistance

B - susceptance

Letter that symbolizes 1/X; Reciprocal of reactance

Y - admittance

Letter representing 1/Z; Reciprocal of impedance

GB plane

R and Z

Which two sides of an impedance triangle for the phase angle in a series circuit

G and Y

Which triangle sides form the phase angle in a parallel circuit

Currents

Voltages can be vectored in series circuits what can be vectored in parallel circuits?

Resistor

Across what component in a resonant circuit is the source voltage drop value developed

Melt L C circuit, blow fuses, start fire

What might happen if a low resistance, resonant circuit were connected across a power line?

Fly wheel affect

What are electron alternations in an anti-resonance circuit called

Anti resonance circuit

• This is also called a parallel circuit where the inductive and capacitive currents cancel each other.

• The inductive and capacitive reactants are still equal, but since they cancel each other, the input impedance becomes maximum

• Thus the source current becomes minimum

• It’s main behavior is as a rejector (rejector circuits)

Q of reactances

Capacitance or C

Which would have higher Q because it has less loss

Which would have the greater effect on the Q of an LC circuit

L or Inductance

Distributed capacitance

The name of the capacitance between turns of a coil

Current

Which dips first with increased coupling? This is because the 2 coupling circuits exchange energy. At certain frequencies, The current induced between the circuits can have opposite phases and partially cancel, so the current can decrease sharply.

Wave trap

circuit that is designed to block or reject a particular frequency (or narrow range of frequencies) while allowing other frequencies to pass.

It’s essentially a frequency-selective circuit: Bandstop

A common one uses an LC circuit.

Ro - characteristics impedance

fc - resonant frequency

For an unbalanced (T-type) low-pass filter, the component values are:

characteristics of constant-k and m-derived filter

Infinity

What is the m value of a high-Q wave trap

1

What is the value of a constant-k LP filter?