What electrical component opposes the flow of current in a DC circuit?
-
Inductor
-
Correct AnswerResistor
-
Voltmeter
-
Transformer
It may help to remember RESISTor as a synonym for oppose, as in oppose the flow of current
Resistor Symbol
https://en.wikipedia.org/wiki/Resistor
Remember, an inductor opposes a CHANGE in current, i.e. an alternating current (AC) - this question is only concerned about direct current (DC).
Last edited by zorba. Register to edit
What electrical parameter is controlled by a potentiometer?
-
Inductance
-
Correct AnswerResistance
-
Capacitance
-
Field strength
A Potentiometer is sometimes called a variable resistor; the schematic symbol
looks just like a resistor (a line with a section in the middle that is jagged
up and down before continuing straight), but has an arrow pointing
perpendicular at the center of the symbol (at the zig-zag section).
Potentiometer Symbol
Potentiometers usually have three poles, one on each side (with the total resistance of the potentiometer between them) and one in the middle which moves back and forth. The total resistance from the middle terminal to an edge is the inverse of the resistance from the middle to the other edge, meaning that as you slide, turn, or otherwise adjust the potentiometer the resistance on one side grows while the other shrinks.
Take a look at the wikipedia article for more information.
Last edited by rjstone. Register to edit
What type of electrical component consists of two or more conductive surfaces separated by an insulator?
-
Resistor
-
Potentiometer
-
Oscillator
-
Correct AnswerCapacitor
A Capacitor is an electrical component that stores energy in an electric field. It consists of at least two conductors separated by an insulator (or dielectric).
The schematic symbol looks just like its construction.
When voltage is applied to the capacitor it will initially pull a lot of current, dropping the voltage and slowly charging up an electric field (due to the difference in potential between the positive and negative charges on the capacitor). Capacitors thus store energy in the electric field, and once they have charged up they no longer allow current to pass through.
If the power source (such as a battery) is removed, the capacitor will begin to discharge, initially keeping the circuit at exactly the same voltage as before with the current dying down until the voltage can no longer be maintained with the energy remaining in the electric field. For this reason, we say that a capacitor resists change in voltage.
Note that this question is vague and that resistors and potentiometers could also be described similarly. It should probably be amended.
Last edited by groydutsmah. Register to edit
What type of electrical component stores energy in a magnetic field?
-
Resistor
-
Capacitor
-
Correct AnswerInductor
-
Diode
There are two questions in the pool that are very similar; one asks about a component storing energy in an electric field, the other in a magnetic field. The magnetic field is an inductor; it generally consists of a coil of wire.
The inductor symbol looks very much like its construction.
The characteristics of the inductor vary drastically depending on whether or not the wire has a ferrite (susceptible to magnetism) core inside; if it does, the ferrite core becomes itself a magnet. This is how electromagnets are made, such as in the classic electronics experiment of wrapping insulated wire around a nail and turning it into an electromagnet.
When current is applied to an inductor, it initially resists the current's flow because of the magnetic field that is generated as the current begins to move through the coil; as the magnetic field charges up, the resistance to the current weakens until the current flows as though through a straight wire. However, when the current source is removed the magnetic field will begin to discharge, keeping the current constant for as long as it can, increasing the voltage until the energy runs out. This is why inductors (including transformers) can be used to build "shockers", or small electronic devices that can produce enough voltage to shock someone, but without enough current to injure them (but hurt them in the case of tazers). The inductor as it discharges pushes the voltage up until it can jump the gap and "spark".
If you can remember that an inductor is a coil of wire and that a coil around a nail creates an electromagnet, then you should be able to remember that an inductor stores energy in a magnetic field.
Mnemonic (memory) hint: Think of "MICE." (M)agnetic field, (I)nductor. (C)apacitor, (E)lectric field.
Last edited by rjstone. Register to edit
What electrical component usually is constructed as a coil of wire?
-
Switch
-
Capacitor
-
Diode
-
Correct AnswerInductor
An inductor generally consists of a coil of wire.
The schematic symbol looks very much like its construction.
The characteristics of the inductor vary drastically depending on whether or not the wire has a ferrite (susceptible to magnetism) core inside; if it does, the ferrite core becomes itself a magnet. This is how electromagnets are made, such as in the classic electronics experiment of wrapping insulated wire around a nail and turning it into an electromagnet.
When current is applied to an inductor, it initially resists the current's flow because of the magnetic field that is generated as the current begins to move through the coil; as the magnetic field charges up, the resistance to the current weakens until the current flows as though through a straight wire. However, when the current source is removed the magnetic field will begin to discharge, keeping the current constant for as long as it can, increasing the voltage until the energy runs out. This is why inductors (including transformers) can be used to build "shockers", or small electronic devices that can produce enough voltage to shock someone, but without enough current to really hurt them. The inductor as it discharges pushes the voltage up until it can jump the gap and "spark".
Last edited by rjstone. Register to edit