DC Circuit Flashcards
The best place to use a wirewound
resistor is:
A. In a high-power, direct-current circuit.
B. In a radio-frequency amplifier.
C. When the resistor doesn’t dissipate much
power.
D. In a high-power, radio-frequency circuit.
A. In a high-power, direct-current circuit.
Wire-wound resistor offers high wattage rating but one of its main disadvantage is this being reactive.
Inductive reactance will be a problem using this resistor at high frequencies. Therefore it is good for high-power applications,but not for high-frequency applications.
(DC means frequency = 0; radio
frequency means high frequency)
Which of the following statements is
true?
A. there is no correlation between the
physical size of a resistor and its
resistance value
B. resistors are always made from carbon
C. the shelf life of a resistor is about 1 year
D. resistors always have axial leads
A. there is no correlation between the
physical size of a resistor and its
resistance value
Physical size is in the wattage rating
related and not in the resistance value.
Which tolerance rating would a low-
quality resistor have?
A. 20%
B. 5%
C. 10%
D. 0.1%
A. 20%
The actual value could vary wildly from
the nominal value: a wide tolerance.
Kirchhoff’s Current law is based on law
of conservation of
A. energy
B. momentum
C. charge
D. mass
C. charge
Kirchhoff’s current law is based on the
law of conservation of charge i.e,
charge that flows in = charge that flows
out.
At DC, inductor acts as______
A. both Open and Short Circuit
B. Neither Open nor Short Circuit
C. Short circuit
D Open circuit
C. Short circuit
At DC, the inductor acts as a short
circuit because the inductive resistance is zero. The frequency of a DC circuit is 0.
The inductive resistance=(2pif*L).
Therefore, if the frequency is 0, the
inductive resistance is zero and it acts
as a short circuit.
Initially, when the switch in a series RL
circuit is closed, the current in the
inductor is?
A. Maximum
B. Infinity
C. Minimum
D. Zero
D. Zero
Initially, when the switch in a series RL
circuit is closed, the inductor acts as an open circuit. Current in an open circuit is zero, hence the inductor current is zero.
With the four band resistor color code,
gold in the third stripe corresponds to a
A. fractional multiplier of 0.1
B. resistor tolerance of ±10%
C. fractional multiplier of 0.01
D. decimal multiplier of 10
A. fractional multiplier of 0.1
FOUR-BAND COLOR
CODING FOR RESISTOR
1st color/band - 1st digit
2nd color/band - 2nd digit
3rd color/band - multiplier/# of zeroes
4th color/band - tolerance
Many resistors connected in series will?
A. Divide the current proportionally
B. Increase the source voltage in proportion
to the values of the resistors
C. Reduce the power to zero
D. Divide the voltage proportionally
among all the resistors
D. Divide the voltage proportionally
among all the resistors
In a series circuit, the current remains
the same across all resistors hence the voltage divides proportionally among all resistors.
If two equal-value capacitors are
connected in parallel, what is their total
capacitance?
A. The same as the value of either capacitor
B. The value of one capacitor times the value
of the other
C. Half the value of one capacitor
D. Twice the value of one capacitor
D. Twice the value of one capacitor
When capacitors are connected in
parallel, the total capacitance is equal to
the sum of the capacitance of each of
the capacitors.
A metal-film resistor:
A. Has considerable inductance.
B. Can dissipate large amounts of power.
C. Is made using solid carbon/phenolic paste.
D. Has less reactance than a wirewound
type.
D. Has less reactance than a wirewound
type.
Some advantages of film resistors: wide
range of values, non-reactive, less
sensitivity to temperature and aging,
and it generates less noise.
At a frequency of 95 MHz, the best form
for an inductor would be:
A. Neither of the choices.
B. Pot core.
C. Either of the choices.
D. Air-core.
D. Air-core.
95 MHz is a very high frequency of
operation. Ferromagnetic-core coil is
not the good option for operating at this
temperature since, hysteresis loss will
be a problem. Therefore, the answer will
be Air-core coil.
(Hysteresis loss is one of the losses
experienced by ferromagnetic-core coil.
This loss increases as the frequency
increases.)
What is the coupling coefficient when
there is ideal coupling?
A. 1
B. 0
C. 100
D. Insufficient information provided
A. 1
When all the flux of coil 1 links with coil 2 it is known as an ideal coupling where the coupling coefficient is 1.
In a closed circuit with a capacitor,
current will continue to flow until the voltage charge across the capacitor plates:
A. Becomes equal to the resistance of the
plates.
B. Becomes greater than the source voltage.
C. Becomes less than the source voltage
D. Becomes equal to the source voltage.
D. Becomes equal to the source voltage.
A capacitor stores electrons like a
battery, and will charge up to source
voltage.
An advantage of a rheostat over a
potentiometer is that:
A. A rheostat works better with dc.
B. A rheostat can handle higher frequencies.
C. A rheostat is more precise.
D. A rheostat can handle more current.
D. A rheostat can handle more current.
Rheostat and potentiometer both offers variable resistances. One advantage of rheostat over the potentiometer is its current capacity.
Rheostat can handle more current than a potentiometer.
A rheostat is______
A. A three-terminal device that divides voltage
B. A two terminal device that divides voltage
C. A two-terminal device that controls
current
D. A three-terminal device that controls
current
C. A two-terminal device that controls
current
A rheostat is a two-terminal variable resistor which is used to control current. They are able to vary the resistance in a circuit without interruption.
The construction is very similar to the construction of a potentiometers.
