DX6ARC - Amateur Radio Club of Capiz

[Information] : Where a question shows [Information]. All the information given below that question is OK

What is a transistor? [Information]
1. A bipolar transistor is an electronic component known as a semiconductor.....There are two type of transistors: NPN Transistor and PNP Transistor......Early transistors were made with germanium but silicon is used almost universally in semiconductor manufacturing...The transistor has three terminals, the emitter, collector and base... It works by transferring a high resistance input to a lower resistance output...The transfer of resistance gave rise to the name trans - istor.
2. Transistors are semiconductor devices used in circuits to either amplify or switching electrical signals or electrical power.
3. Three of the most fundamental transistor amplifiers are: common emitter, common collector and common base.
Field Effect Transistor (FET) : [Information]
1. The field-effect transistor (FET) is a type of transistor which uses an electric field to control the flow of current.... FETs are devices with three terminals: source (S), gate (G), and drain (D).... FETs control the flow of current by the application of a voltage to the gate, which in turn alters the conductivity between the drain and source.....The FET also has a high input impedance.
2. Q : What is FET used for?
  A : The FET is commonly used for weak-signal amplification (for example, for amplifying wireless signals). The device can amplify analog or digital signals. It can also switch DC or function as an oscillator.....FETs suitable for switching analog signals.
3. A field-effect transistor (FET) consists of a channel of N- or P-type semiconductor material through which current can flow, with a different material (laid across a section of the channel) controlling the conductivity of the channel.
4. One end of the channel is known as the source, the other end of the channel is called the drain, and the control mechanism is called the gate. By applying a voltage to the gate, you control the flow of current from the source to the drain. Leads are attached to the source, drain, and gate.
Vacuum tube : [Information]
1. In electronics, a vacuum tube, an electron tube, or valve is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied and is used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space.Types of vacuum tubes include : Diode : Triode : Tetrode : Pentode and Cathode Ray Tubes (CRT) etc
2. Cathode or Filament(Negative Electrode) : an electrode which is heated to make it emit electrons due to thermionic emission.
3. Anode or Plate (Positive Electrode) : will attract those electrons emitted by the cathode if it is at a more positive voltage. The result is a net flow of electrons from the filament (cathode) to plate (andode).
4. Grid : The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode. The grid is used to control the flow of electrons from the cathode to the anode (plate) electrode.
In a vacuum tube, the measure of ________ is the ratio of the electrical current change at an output port as compared to the voltage change at the input port.
1. resistance
2. transconductance
3. conductance
4. inductance
What is a diode ? [Information]
1. A diode is a semiconductor device that essentially acts as a one-way switch for current. It allows current to flow easily in one direction, but severely restricts current from flowing in the opposite direction.
  
  The size of the barrier voltage at the p-n junction is depends on, the amount of doping, junction temperature and type of material used. The barrier voltage for silicon diode is 0.7 volts and for germanium is 0.3 volts.
2. What can a diode be used for?
  Diodes can be used as rectifiers, signal limiters, voltage regulators, switches, signal modulators, signal mixers, signal demodulators, and oscillators. The fundamental property of a diode is its tendency to conduct electric current in only one direction.
3. Types of diode include : Zener : Light emitting (LED) : PIN : Tunnel: PNJunction : Schottky etc
4. A diode has two terminals. The positive side is called the anode and the negative one is called the cathode.....The stripe (any contrasting color) corresponds to the diode's cathode.
A vacuum tube having anode, cathode, and grid is called:
1. diode
2. pentode
3. triode
4. tetrode
Operational amplifier (Op-amp) is an integrated circuit (IC) : [Information]
1. An operational amplifier (often op-amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.
2. Operational amplifiers. Amplifiers are devices which take a relatively weak signal as an input and produce a much stronger signal as an output
3. An Operational Amplifier or op-amp for short, is fundamentally a voltage amplifying device designed to be used with external feedback components such as resistors and capacitors between its output and input terminals.
Commonly used diode as RF switch
1. FET
2. PIN
3. IC
4. JFET
The three terminals of the silicon control rectifier (SCR) are the anode, cathode and ______
1. channel
2. gate
3. emitter
4. carrier
Type of diodes normally used in voltage regulator circuits
1. amplifier
2. bias
3. zener
4. pin
What is the forward resistance of an ideal diode
1. zero
2. medium
3. infinity
4. some
Varactor Diode (varicap diode) : [Information]
1. Varactor diode is a p-n junction diode whose capacitance is varied by varying the reverse voltage.
2. Varactor diodes are commonly found in communication equipment where electronic tuning is a necessity. They are an important component of radio frequency or RF applications.
A transformer is a static electrical device that transfers electrical energy between:
1. two or more circuits.
2. copper wiring
3. variable resistors
4. two or more capacitors
The junction gate field-effect transistor is known as _________
1. winfet
2. amfet
3. mosfet
4. jfet
A commonly used sensing mechanism used in DC ammeters, voltmeters, and ohm meters is a current-sensing device called a ___________
1. D'Arsonval meter movement.
2. amfet
3. mosfet
4. jfet
Resistance (R): Conductance (G) : [Information]
1. Resistance is the opposition that a substance offers to the flow of electric current. When an electric current of one ampere passes through a component across which a potential difference (voltage) of one volt exists, then the resistance of that component is one ohm...The unit of resistance is Ohm (Ω)
2. Conductance is the measure of how easily electricity flows along a certain path through an electrical element, and since electricity is so often explained in terms of opposites, conductance is considered the opposite of resistance....The unit of conductance is Siemens (S) or mho.
Inductance : [Information]
1. Inductance is the ability of an inductor to store energy and it does this in the magnetic field that is created...The unit of inductance is the henry (H)
2. A current generated in a conductor by a changing magnetic field is proportional to the rate of change of the magnetic field. This effect is called Inductance and is given the symbol L
3. One henry is the amount of inductance necessary to induce one volt when the current in coil changes at a rate of one ampere per second.
Field Effect Transistor (FET) [Information]
1. N channel Junction Field Effect Transistor (j-FET) comprises a channel of N material surrounded by a ring of P material; P channel is the opposite
2. Current flow along the channel between source (S) and drain (D) is controlled by the gate (G) voltage
3. A small change in gate voltage causes a large change in drain current; the ratio g (mA÷V) is called the transconductance
4. The two basic types of field effect transistors (FET) are....N and P channel
The sub-harmonic of 1000 kHz
1. 500 kHz
2. 1000 kHz
3. 1500 kHz
4. 2000 kHz
A conductive circuit pattern applied to one or both sides of an insulating substrate is known as
1. insulator circuit board
2. printed circuit board (PCB)
3. out board
4. chess board
3 db points are also known as
1. full-power points
2. quarter-power points
3. half-power points
4. one and half power points
What is the capacitive reactance (XC) when the capacitor value is 350 μF and the operating frequency 1200 Hz?
1. 0.379 ohms
2. 0.385 ohms
3. 0.390ohms
4. 0.400 ohms
A series circuit consists of an inductance of 400 uH and a capacitance of 400 uF. What is the resonant frequency (f)?
1. 384.9 Hz
2. 397.9 Hz
3. 400.8 HZ
4. 410.2 Hz
The majority carrier in P-type semiconductor materials
1. holes
2. electrons
3. particles
4. atoms
What is the majority carrier in N-type semiconductor material?
1. amperes
2. holes
3. electrons
4. volts
A Triac is a three terminal semiconductor device used for controlling:
1. resistance
2. voltage
3. current
4. capacitance
Tunnel Diode : [Information]
1. Tunnel Diode is the P-N junction device that exhibits negative resistance. When the voltage is increased then the current flowing through it decreases. It works on the principle of Tunneling effect.
2. The tunnel diode is capable of fast operation and can function well into the microwave radio frequency band.
3. Tunnel diode can be used as a switch, amplifier, and oscillator.
In NPN transistor, the majority charge carriers are ____
1. protons
2. carriers
3. electrons
4. holes
A common semi-conductor diode used as radio frequency switch
1. PIN
2. SSD
3. JFET
4. FET
A type of semi-conductor diode having a negative resistance region
1. Tunnel
2. Bridge
3. Positive
4. Resistance
An electronic semi-conductor component capable of controlling electron flow through it is known as
1. vacuum tube
2. barrier device
3. solid-state device
4. resistance device
A disadvantage of using semi-conductor as against vacuum tubes
1. medium heat resistance
2. high heat resistance
3. thermal heat resistance
4. low heat resistance
Doping germanium with gallium causes
1. hole current flow
2. positive current flow
3. negative current flow
4. electron current flow
Solid state lamps are also known as
1. LSE
2. LED
3. LDE
4. LES
An emitter follower transistor amplifier circuit is also known as
1. common-receiver
2. common-transmitter
3. common-collector
4. common-electronic
A photodiode is a semiconductor device that converts light into an electrical _______
1. current
2. voltage
3. inductance
4. resistance
The three basic parts of transistors are the base, the collector and the
1. bias
2. gate
3. emitter
4. junction
A varactor is variable _______ diode
1. capacitor diode
2. resistor diode
3. zener diode
4. junction diode
Resistors : [Information]
1. A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses
2. Standard resistors have four bands. These resistors have two bands for the resistance value, third band is the multiplier and the forth band the tolerance band.
3. Precision resistors have five bands.These have three bands for the resistance value, the fourth band is the multiply factor and the fifth band represents the tolerance
4. An ohm (Ω) is the resistance that occurs when a current of one ampere passes through a resistor with a one volt drop across its terminals. The current is proportional to the voltage across the terminal ends.
Zener diodes are diodes
1. that operate on its downward voltage
2. that operate on its capacity voltage
3. that operate on its avalanche voltage
4. that operate on its thermal voltage
What is a digital integrated circuit (IC) ? [Information]
1. The abbreviation IC stands for "integrated circuit" and in practice denotes any semiconductor-based chip comprising an integrated set of digital circuitry. ... A standard logic IC is a single, small, integrated package carrying basic components and common functionalities for a logic circuit.
2. Integrated circuit (IC), sometimes called as a chip or microchip, is a semiconductor wafer on which a thousand or millions of tiny resistors, capacitors, and transistors are fabricated. An IC can be a function as an amplifier, oscillator, timer, counter, computer memory, or microprocessor.
The two very useful semi-conductors are germanium and
1. Bromide
2. Basalt
3. Silicon
4. Magnesium
Parallel circuit consists of an inductance of 10 uH and a capacitance of 500 uF. What is the resonant frequency (f) ?
1. 3.56 kHz
2. 6.00 kHz
3. 7.38 kHz
4. 2.25 kHz
A feature common to vacuum tubes and transistors is that both:
1. can amplify signals
2. have electrons moving through a wire
3. convert electrical energy to radio waves
4. use heat to cause electron movement
Transistor current gain [Information]
1. Current gain (β – Beta) is the ratio of change in collector current for change in base current
2. β can be 500 or more
Fuse : [Information]
1. In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it. When a fuse has blown it removes electrical power from an electrical circuit.
  
  Most fuses are marked on the body or end caps with markings that indicate their ratings.
  Current rating of the fuse
  Voltage rating of fuse
2. When a fuse has blown ?
  It removes electrical power from an electrical circuit
3. What happens if the fuse has a rating higher than the permitted rating of the wiring?
  Then the fuse will not blow out even the current rises above the permitted value. Such a fuse remains the circuit close and allows the current to flow beyond the limit permitted to the wiring or other components
The cathode-ray tube (CRT) is _____
1. A vacuum tube that contains one or more electron guns and a phosphorescent screen, and is used to display images. It modulates, accelerates, and deflects electron beam(s) onto the screen to create the images.
What is the inductive reactance (XL) when the inductance value is 1 mH and a frequency of 6 kHz?
1. 28.9 ohms
2. 37.7 ohms
3. 40.4 ohms
4. 42.7ohms
Series circuit consists of an inductance of 500 uH and a capacitance of 400 pF. What is the resonant frequency ?
1. 356 kHz
2. 500 KHz
3. 70 Mhz
4. 89 MHz
The beta of a transistor is its ______
1. current amplification factor
2. resistance amplification factor
3. voltage amplification factor
4. capacitance amplification factor
In PNP transistor, the majority charge carriers are ____
1. holes
2. protons
3. conductors
4. electrons
A _________ is a vacuum tube having five active electrodes:
1. diode
2. pentode
3. Triode
4. tetrode
A diode is a two-terminal electronic component that conducts current primarily in ________
1. two - directions
2. one direction
3. both directions
4. multi - directions
The electrodes of a semi- conductor diode are known as:
1. anode and cathode
2. gate and source
3. cathode and drain
4. collector and base
In a diode current can flow from:
1. grid to anode
2. cathode to anode
3. cathode to grid
4. anode to cathode
The two basic types of bipolar transistors are:
1. P and N channel types
2. NPN and PNP types
3. diode and triode types
4. varicap and zener types
A transistor can be destroyed in a circuit by:
1. cut-off
2. excessive light
3. saturation
4. excessive heat
The two basic types of field effect transistors (FET) are:
1. NPN and PNP
2. germanium and silicon
3. inductive and capacitive
4. N and P channel
A fuse is used....
1. to dissapate heat
2. as an electronic filter
3. as a safety device for protecting an electrical system
4. to transform a high to a low voltage
Quartz Crystal [Information]
1. Quartz crystals maintain a precise frequency standard...They can be used as oscillators in radios....timepieces (clocks and watches).....Provide frequency stability.
2. Radios can use crystal filters made from quartz crystals. Crystal filters have a fixed bandwidth and mostly cannot be adjusted.
3. In operation the quartz crystal uses the piezoelectric effect. When voltage is applied across a piezoelectric crystal, it vibrates at the frequency of the applied voltage.
4. Conversely, if we apply a mechanical force to vibrate the crystal, it generates an AC voltage of the same frequency.
7400 and 4000 integrated circuits : [Information]
1. The 7400 series of transistor–transistor logic (TTL) integrated circuits are the most popular family of TTL integrated circuit logic.It contains four independent two-input NAND gates.
2. The 4000 series is a range of CMOS (Complementary Metal Oxide Semiconductor) ICs. The CMOS circuitry means that 4000 series ICs are static sensitive.
Capacitor : [Information]
1. A capacitor has the ability of being able to store energy in the form of an electrical charge....It consists of at least two electrical conductors separated by a distance.
2. Capacitance is defined as being that a capacitor has the capacitance of 1 Farad when a charge of 1 Coulomb is stored across its plates by a voltage of 1 volt
3. An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor.
4. Electrolytic capacitors have a positive and negative connections.The positive connection has longer pin (anode) and the other connection a shorter, negative pin (cathode)....There is also a large stripe or a minus sign (or both) on one side of the capacitor. The lead closest to that stripe or minus sign is the negative lead, and the other lead (which is unlabeled) is the positive lead.
Which diodes are normally reversed biased?
1. pin diode
2. emitter diode
3. zener diode
4. alpha diode
The symbol used for current amplification factor of transistors is
1. alpha
2. beta
3. delta
4. gamma
A circuit element that opposes change in current
1. switch
2. capacitor
3. resistor
4. inductor
If the radiation resistance of the antenna is 5000 ohms, the power radiated is 125 kilowatts, what is the antenna current?
1. 3 A
2. 5 A
3. 7 A
4. 10 A
Silicon controlled rectifier (SCR) : [Information]
1. Is a four-layer solid-state current-controlling device and has three terminals.
2. SCRs are unidirectional devices (i.e. can conduct current only in one direction) .
3. The SCR has Anode and Cathode terminals like a conventional diode and a third control terminal, referred to as the Gate
4. SCR is a device that is widely used for controlling or switching power and often high voltage AC or DC circuits.
Neon Lamp : [Information]
1. A neon lamp (also neon glow lamp) is a miniature gas discharge lamp. The lamp typically consists of a small glass capsule that contains a mixture of neon and other gases at a low pressure and two electrodes (an anode and a cathode)
2. Small neon lamps are most widely used as visual indicators in electronic equipment and appliances, due to their low power consumption, long life, and ability to operate on mains power.
Vidicon : [Information]
1. A small television camera tube, used in closed-circuit television and outside broadcasts, in which incident light forms an electric charge pattern on a photoconductive surface. Scanning by a low-velocity electron beam discharges the surface, producing a current in an adjacent conducting layer
2. A vidicon is sensitive, so it can see things in dim light. But the dimmer the light gets, the slower the vidicon responds to changes in the image.
A _________ is a vacuum tube having four active electrodes:
1. Pentode
2. Diode
3. Tetrode
4. Triode
Zener Diode : [Information]
1. A Zener diode is a type of semiconductor diode that is different to a normal diode as it allows current to flow from its anode to its cathode in either a forward or reverse direction, but only when exposed to enough voltage.
2. Zener diodes are designed to change the direction of current flow once the voltage reaches a specific, defined voltage level. This also means that Zener diodes can operate continuously in a breakdown mode
3. What is a typical application of Zener diodes?
  Zener diodes are used in all kinds of electronic equipment and are used to protect circuits from overvoltage and electrostatic discharge or for switching applications.
4. Zener Diode Regulator : Zener Diodes can be used to produce a stabilised voltage output with low ripple under varying load current conditions.....Whereas diodes are used for rectification.
The two very useful semi-conductors are germanium and
1. Bromide
2. Basalt
3. Silicon
4. Sodium
Power Supply Type Diode Rectifiers: [Information]
1. Power Diodes are semiconductor pn-junctions capable of passing large currents at high voltage values for use in rectifier circuits
2. Power diodes can be used individually or connected together to produce a variety of rectifier circuits such as “Half-Wave”, “Full-Wave” or as “Bridge Rectifiers”
3. Power rectifiers are electrical devices that convert alternating current (AC) to direct current (DC).
A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. [Information]
1. in the basic PLL, reference signal and the signal from the voltage controlled oscillator are connected to the two input ports of the phase detector. The output from the phase detector is passed to the loop filter and then filtered signal is applied to the voltage controlled oscillator.
2. the phase locked loop or PLL is a particularly useful circuit block that is widely used in radio frequency or wireless applications.
3. FM demodulation: One major phase locked loop application is that of a FM demodulator.
Light-emitting diode (LED) : [Information]
1. A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated.
2. Common uses: indication lights on devices, small and large lamps, traffic lights, large video screens, signs etc
3. Anode has the longer lead and is positive.....Cathode has the shorter lead and is negative.....The lead nearest the flat edge of the LED will be the negative, cathode lead.
Triac : [Information]
1. The triac is a three-terminal semiconductor switching device that is used for controlling current flow in a circuit..... It is a bidirectional device that can pass the current in both forward and reverse direction when triggered
2. Triacs uses include light dimmers for domestic lighting, motor control, electronic switches,speed controls for electric fans and heaters etc.
3. The triac terminals are.......Anode 1, Anode 2 and Gate.
  Anode 1 and Anode 2 are normally termed Main Terminal 1 (MT1) and Main Terminal 2 (MT2) respectively.
Transformers : [Information]
1. A transformer is a device that uses the principles of electromagnetism to convert one voltage or current to another. It consists of a pair of insulated wire wound around a magnetic core. The winding to which the voltage or current to be converted is called the primary winding and the output winding is called the secondary winding.
2. Transformers can – step up, which increases the voltage or current or impedence and step down, which decreases the voltage or current or impedence input.
3. A transformer consists of two electrically isolated coils and operates on Faraday's principal of “mutual induction”, in which an EMF is induced in the transformers secondary coil by the magnetic flux generated by the voltages and currents flowing in the primary coil winding.
4. Note: Transformers work only with changing or AC voltages and do not work with DC.....The primary is always connected to the source of power, the secondary is always connected to the load and either the high- or low-voltage winding can be the primary or the secondary.
Schottky diode or Schottky barrier diode or Hot-Carrier diode : [Information]
1. It is a semiconductor diode with a very fast switching action, but a low forward voltage drop.....The forward voltage drop ranges from 0.3 volts to 0.5 volts (0.15 to 0.45volts)
2. It is a unilateral junction. A metal semiconductor junction is formed at one end and another metal semiconductor contact is formed at the other end
3. Schottky diode are also used as rectifiers in switched-mode power supplies :RF mixer and detector diode and can be used in high-speed switching applications.
4. Schottky diode advantages:
  Low turn on voltage:
  Low junction capacitance:
  Fast recovery time:
PIN diode : [Information]
1. Three of the applications for PIN diodes.
  High voltage rectifier: The PIN diode can be used as a high voltage rectifier.
  RF switch: The PIN diode makes an ideal RF switch.
  Photodetector: The PIN diode is used for converting the light energy into the electrical energy.
2. The anode and cathode are the two terminals of the PIN diode. The anode is the positive terminal and cathode represent their negative terminals.
P-N Junction Diode : [Information]
1. A p-n junction diode is a electronics component basic semiconductor device that controls the flow of electric current in a circuit. It made from a combination of a P-type and N-type semiconductor material, known as a p-n junction, with leads attached to the two ends...It has a positive (p) side and a negative (n) side
2. Forward bias : When a voltage source is connected to a diode such that the positive side of the voltage source is on the anode and the negative side is on the cathode, the diode becomes a conductor and allows current to flow.
Types of electronic components :The electronic components are generally classified into two types Passive and Active : [Information]
1. Passive components :The electronic component, which consumes energy in the form of voltage from the source, but does not produce or supply energy is called passive electronic component and are not depend on a external power supply.
2. The different types of passive components include resistors, capacitors, and inductors.
3. Active components :The electronic component, which consumes energy in the form of voltage or current and produces or supplies energy in the form of electric current or voltage is called active component.... Require a external power source and use the power supply to boost or amplify the output signal.
4. The different types of active components include diodes, transistors, and integrated circuits (IC).
Unijunction Transistor (UJT) : [Information]
1. A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch. The UJT is not used as a linear amplifier.
2. The most common application of a unijunction transistor is as a triggering device for SCR's and Triacs but other UJT applications include sawtoothed generators, simple oscillators, phase control, and timing circuits. The simplest of all UJT circuits is the Relaxation Oscillator producing non-sinusoidal waveforms.
The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) [information]
1. The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor is a semiconductor device which is widely used for switching and amplifying electronic signals in the electronic devices. ... The MOSFET is a four terminal device with source(S), gate (G), drain (D) and body (B) terminals.....The body is frequently connected to the source terminal, reducing the terminals to three. It works by varying the width of a channel along which charge carriers flow (electrons or holes).
2. MOSFETs are tri-terminal, unipolar, voltage-controlled, high input impedance devices.
3. The MOSFET has an extremely high input gate resistance with the current flowing through the channel between the source and drain being controlled by the gate voltage.
4. Depletion Type: The transistor requires the Gate-Source voltage (VGS) to switch the device “OFF”. The depletion-mode MOSFET is equivalent to a “Normally Closed” switch.
  
  Enhancement Type: The transistor requires a Gate-Source voltage(VGS) to switch the device “ON”. The enhancement-mode MOSFET is equivalent to a “Normally Open” switch
Voltage drop across Silicon and Germanium diodes [Information]
1. The voltage dropped across a conducting forward-biased diode is called the forward voltage.
2. Germanium diodes have a forward voltage of approximately 0.3 volts.
3. A forward -biased silicon diode has about 0.7 V across it.
A semiconductor is said to be doped when small quantities of the following are added:
1. protons
2. electrons
3. impurities
4. ions
A low-level signal is applied to a transistor circuit input and a higher-level signal is present at the output. This effect is known as:
1. amplification
2. detection
3. modulation
4. rectification
The Light-Emitting Diode [Information]
1. If the semiconductor material and doping are appropriately chosen, the energy state transition around the junction can emit electromagnetic energy. Such a diode is known as a light-emitting diode (LED).
2. An LED (Light Emitting Diode) emits light when an electric current passes through it. ... The ballast resistor is used to limit the current through the LED to prevent the LED from burning out
3. Typically, the forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the color of the LED.
Transformer : Turns, Voltage, Current and Power Ratio (Tr) [Information]
1. The turns ratio of a transformer specifies the relative number of turns on the primary and secondary windings.
  The number of turns on the primary is always specified first. For example, a 5:1 transformer has five times as many turns on the primary as on the secondary. A 1:3 transformer has three times as many turns on the secondary as on the primary.
  
  Voltage across the primary (Vp) : Current in the primary (Ip) : Power into primary (Pp) : Turns on primary (Np)
  Voltage across the secondary (Vs) : Current in the secondary (Is) : Power out secondary (Ps) : Turns on secondary (Np)
2. Voltage (V) Ratio : The ratio of the voltage on the primary winding to the voltage on the secondary winding is the same as the ratio of the number of turns on the primary winding to the number of turns on the secondary winding (the turns ratio).
  The voltage ratio relationship can be written as follows: Vp / Vs = Np / Ns or Vp x Ns = Vs x Np
3. Current (I) Ratio : The ratio of the current in the secondary to the current in the primary is the same as the ratio of the number of turns in the primary to the number of turns in the secondary (the turns ratio). Note: This is the opposite way round to the voltage ratio.
  Current ratio relationship can be written as follows: Is / Ip = Np / Ns or Is x Ns = Ip x Np
4. Power Ratio : The total power coming out of the transformer must the same as the power flowing into it (neglecting minor losses). Therefore, if the voltage increases, the current must decrease to maintain the same total power. Likewise, if the output voltage is lower, the output current must be higher to maintain the same power.
  Power (watts) formula = V (volts) x I (current) : Transfomer Power (watts) : Vp x Ip = Vs x Is.
Transformer Examples [Information]
1. The transformer has a turns ratio of 5:20 and the secondary voltage is 100 VAC what is the primary (Vp) voltage ?
  Rearranging the above voltage ratio we get Vp = Vs x Np / Ns = 100 x 5 / 20 = 25 VAC
2. In a mains power transformer, the primary winding has 250 turns, and the secondary has 500. If the input voltage is 110 volts, the likely secondary voltage would be ? Rearranging the voltage ratio : Vs = Vp x Ns / Np = 110 x 500 / 250 = 220 volts.
  
  A transformer has a 240 volt primary that draws a current of 250 mA from the mains supply. Assuming no losses, what current would be available from a 12 volt secondary? 250 ma = 0.25A. rearranging the power formula : Is = Vp x Ip / Vs = 240 x 0.25 / 12 = 5 amperes.
3. 240 VAC is applied across the primary of a 20:1 transformer and current flowing in the primary is 1A. The power in and power out ?
  To use the transformer power ratio Vp x Ip (Pp) = Vs x Is (Ps), we need to find Vp, Vs, Ip and Is, we already have Vp (240 VAC), Ip (1A) and a ratio of 20 turns on the primary and 1 turn on secondary, using the voltage, current and power ratios.
  Vp = 240 VAC : Ip = 1A : Vs = 12 VAC : Is = 20A : Pp = 240 watts : Ps = 240 watts.
4. A 100% efficient transformer has a turns ratio of 1:5. If the secondary current is 50 mA, the primary current is ?
  Ip = Is x Ns / Np = 50 x 5 / 1 = 250 ma or 0.25 A
Where must a fuse be connected in a mains circuit ?
1. the neural wire only
2. the earth wire only
3. the live wire only
73 de 4F3EW - 8 November 2021

DU6MOT • Aklan, Philippines

NTC Class B Element 6 (VI)