1 Answer

Answer :

LEDs normally work on a voltage of 1 to 2 V.

Related questions

Description : 9 leds each of 1 volt drop is series with 9  volt battery , do we need a resistor?(SMD leds) I have seen some smd leds without resistor !

Last Answer : We connect resistor to limit the current. So, it depends upon the current rating of the LED, which is provided by manufacturer.

Description : Will UV LEDs work like a UV tube?

Last Answer : answer:Ahh too late to edit, I can get 385-405nm ones for super cheap, but I can see some 380nm ones for 67 cents each, woud those be better? I'm having trouble finding what the real ... , found 100 5mm LEDs, 380-385nm wavelength, only 30 bucks! I wonder if that wavelength works well though.

Description : Which kind of lightbulb is more energy efficient / cost efficient to operate for the same amount of light: those twisty spiral florecent bulbs or LEDs?

Last Answer : LEDs are more energy efficient and last longer

Description : Is my 1993 Miata Too old school for LED's?

Last Answer : It maybe the bad contact in the socket is is causing it. check your grounds. The circuit for the brake/running lights maybe causing the cruise control to malfunction. I had a Mitsubishi that ... 4 way flashers on and have the cruise control work ! Think flashing lights equal to malfunction socket.

Description : Why can't I mix and match LEDs wired in parallel?

Last Answer : answer:An LED is a diode. As such it has a forward voltage drop, i.e., when it's conducting current and shining light, there is a small voltage drop from one end to the other. (After all, with ... device & some would shine brighter than others. So it's still best to give each LED its own resistor.

Description : Why can't I mix and match LEDs wired in parallel?

Last Answer : answer:An LED is a diode. As such it has a forward voltage drop, i.e., when it's conducting current and shining light, there is a small voltage drop from one end to the other. (After all, with ... device & some would shine brighter than others. So it's still best to give each LED its own resistor.

Description : Has anyone bought loose LEDs?

Last Answer : What are you buying them for? I’ve bought them before, but I was buying them for an electronics kit type thing.

Description : Where can I find the best deals on LEDs?

Last Answer : Here!

Description : Tunnel diode is a: a) Power diode b) Has light doping c) Has heavy doping d) Is a reverse recovery diode Ans: C 76.LEDs are fabricated from: a) Silicon b) Germanium c) Si or Ge d) Gallium arsenide

Last Answer : Ans: D

Description : What is the lifetime of LEDs? a. 200,000 minutes b. 200,000 hours c. 150,000 minutes d. 150,000 hours

Last Answer : b. 200,000 hours

Description : Are the effects of temperature changes on LDs more or less significant than for LEDs?

Last Answer : More.

Description : Which types of LEDs are the preferred optical sources for short-distance, low-data-rate fiber optic systems?

Last Answer : SLEDs and ELEDs.

Description : Why are LEDs preferred over laser diodes for low- and moderate-frequency analog applications?

Last Answer : LEDs require less complex circuitry than lasers.

Description : Semiconductor LEDs emit incoherent light. Define incoherent light

Last Answer : Light waves that lack a fixed-phase relationship

Description : Why can multimode graded-index fiber 1300-nm systems using LEDs operate over longer distances and at higher bandwidths than 850-nm systems?

Last Answer : Longer distances and higher bandwidths are possible because fiber material losses and dispersion are significantly reduced at the 1300-nm region.

Description : LEDs operating at 850 nm provide sufficient optical power for short-distance, low-bandwidth multimode systems. List three conditions that prevent the use of LEDs in longer distance, higher bandwidth multimode systems.

Last Answer : Multimode fiber dispersion, the relatively high fiber attenuation, and the LED's relatively low optical output power.

Description : Both LEDs and ILDs operate correctly with ∙ A. forward bias ∙ B. reverse bias ∙ C. neither forward nor reverse bias ∙ D. either forward or reverse bias

Last Answer : A. forward bias

Description : Why are visible-light LEDs not used for fiber optics? ∙ a. It has high losses ∙ b. It has short wave ∙ c. It has low attenuation ∙ d. It has weak signal

Last Answer : ∙ a. It has high losses

Description : What is the typical wavelength of light emitted from epitaxially grown LEDs? ∙ a. 840 nm ∙ b. 490 nm ∙ c. 480 nm ∙ d. 940 nm

Last Answer : ∙ d. 940 nm

Description : Both LEDs and ILDs operate correctly with ∙ a. Forward bias ∙ b. Reverse bias ∙ c. Neither A or B ∙ d. Either A or B

Last Answer : a. Forward bias

Description : What is the lifetime of LEDs? ∙ a. 200,000 minutes ∙ b. 200,000 hours ∙ c. 150,000 minutes ∙ d. 150,000 hours

Last Answer : a. 200,000 minutes

Description : Both LEDs and ILDs operate correctly with:

Last Answer : Forward bias

Description : Find out number of data lines required to interface 16 LEDs arrange in the 4 x 4 matrix form.

Last Answer : 4+4=8, eight lines are required for 4x4 matrix of 16 LEDs

Description : The semiconductor used for LEDs emitting in the visible range is  (a) GaAs (b) GaAlAs (c) GalnAs (d) GaAsP

Last Answer : The semiconductor used for LEDs emitting in the visible range is GaAsP

Last Answer : The power consumption of LEDS may be of the order of 5 to 10 milli-amperes.

Description : The ground detection system, shown in the illustration for a low-voltage, threephase system has a ground in line 'A'. Therefore, lamp 'A' will burn ____________. EL-0009 A. dimly or be out, and lamps 'B' and ... and 'C' will burn dimly or be out D. brightly, and lamps 'B' and 'C' will burn normally

Last Answer : Answer: A

Description : A three-phase electrical system is equipped with ground detecting lamps. If one of the lamp goes dark and the other two burn normally before and after the test switch is operated, this indicates _______________. ... of the three phases D. the voltage to the dark lamp is less than that of the system

Last Answer : Answer: A

Description : Normally, the FIRST step in troubleshooting a transistor circuit card is to _____________. A. carefully remove the transistors from the card B. give the circuit an initial test with a signal generator C. test for continuity with a low voltage DC supply D. visually inspect the card

Last Answer : Answer: D

Description : Which of the following conditions is most likely to occur if a single element fuse were used to replace a blown dual element fuse in a motor controller circuit? A. The fuse will blow when the motor ... overheats at high motor loads. C. The motor runs at reduced voltage. D. The motor runs normally.

Last Answer : Answer: A

Description : The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains _____________. A. a magnetic operating coil B. normally open line contacts C. thermal-overload protection D. a momentary-contact start button

Last Answer : Answer: D

Description : Telephone companies normally provide a voltage of __________to power telephones. (A) +24 volts DC (B) -24 volts DC (C) +48 volts DC (D) -48 volts DC.

Last Answer : (D) -48 volts DC.

Description : Transmission voltage of ll kV is normally used for distances upto (a) 20—25 km (b) 40—50 km (c) 60—70 km (d) 80—100 km

Last Answer : (a) 20—25 km

Description : A voltage source inverter is normally employed when  (1) source inductance is large and load inductance is small (2) source inductance is small and load inductance is large (3) both source and load inductance are small (4) both source and load inductance are large

Last Answer : 3

Description : Define: i) Input Offset Voltage ii) Input offset Current iii) Input Bias Current iv) Output offset voltage

Last Answer : Definition of parameters of OPAMP is follows:  i) Input Offset Voltage: Input offset voltage is defined as the voltage that must be applied between the two input terminals of an OPAMP to null or ... to ground) and output voltage is obtained non zero such voltage is output offset voltage of opamp.

Description : An SSB transmitter produces a peak-to-peak voltage of 200 V across a 100 Ω antenna load. What is the Peak Envelope Power? A) 49.98 W B) 79.98 W C) 99.96 W D) 199.93 W

Last Answer : An SSB transmitter produces a peak-to-peak voltage of 200 V across a 100 Ω antenna load. What is the Peak Envelope Power? A) 49.98 W B) 79.98 W C) 99.96 W D) 199.93 W

Description : How can we protect circuit from reverse voltage polarity?

Last Answer : We can protect circuit from reverse voltage by connecting diode in series but connecting diode in series is less efficient. So we can also protect circuit from reverse voltages by connecting p channel ... gate and source of mosfet and input voltage is applied between drain and Gate of mosfet.

Description : In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half of the secondary winding is 30 V. Then PIV is: (1) 30 V (2) 60 V (3) 15 V (4) 10 V

Last Answer : In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half of the secondary winding is 30 V. Then PIV is: 60 V

Description : The device used for voltage regulator is

Last Answer : The device used for voltage regulator is zener diode

Description : Pinch off voltage of a J FET is the drain to source voltage above which drain current. • Increases • Decreases • Remains constant • Becomes zero

Last Answer : Pinch off voltage of a J FET is the drain to source voltage above which drain current Remains constant

Description : The ripple voltage in the output of a single phase half wave rectifier with 10 V rectified dc voltage with resistive load and without filter will be • 12.1 volt • 1.21 volt • 0.482 volt • 4.82 volt

Last Answer : The ripple voltage in the output of a single phase half wave rectifier with 10 V rectified dc voltage with resistive load and without filter will be 12.1 volt

Description : The time constant of an RC circuit is defined as the time taken by the voltage across the capacitor to become_____ of its final value   (a) 63.2% (b) 36.8% (c) 50% (d) 100%  

Last Answer : The time constant of an RC circuit is defined as the time taken by the voltage across the capacitor to become 63.2% of its final value 

Description : Threshold voltage for PMOS is generally (A) Negative (B) Positive (C) Zero (D) None of the above

Last Answer : Threshold voltage for PMOS is generally Negative 

Description : What type of instrument is used to measure dc voltage of the order 5 volts? (A) moving iron type (B) electro-static type (C) moving coil type (D) all of these

Last Answer : Permanent Magnet Moving Coil (PMMC) voltmeter is used to  measure the DC voltage. We can also use moving iron meter, but it has more error compared to moving coil.

Description : A step voltage E is applied to a series R-L circuit. The rate of change of current is maximum at t = _:  (1) Zero (2) Infinity (3) L/R (4) R/L 

Last Answer : A step voltage E is applied to a series R-L circuit. The rate of change of current is maximum at t = Zero.

Description : What is the voltage resolution of an 8-stage ladder network?  (1) Vref /128 (2) Vref /256 (3) Vref /512 (4) Vref /1024

Last Answer : Vref /256 is the voltage resolution of an 8-stage ladder network.

Description : An eight bit digital data 10101100 is fed to an ADC. The reference voltage is +10V. The analog output voltage will be:  (1) 1.05V (2) 6.74V (3) 10.10V (4) 5.15V

Last Answer : An eight bit digital data 10101100 is fed to an ADC. The reference voltage is +10V. The analog output voltage will be: 6.74V.

Description : The -------can conduct current in either direction and is turned-on when the breakover voltage is exceeded  A) SCR B) Diac  C) SCS D) Traic

Last Answer : The diac  can conduct current in either direction and is turned-on when the breakover voltage is exceeded.

Description : The voltage regulation of an alternator having 0.75 leading p.f. load, no-load induced e.m.f. of 2400V and rated terminal voltage of 3000V is —————————————  A) 20% B) —20% C) 150 D) -26.7

Last Answer : -20

Last Answer : A Zener diode is operated in the Reverse bias around the knee of breakdown region mode as a voltage stabilizer.