Electric current – part (2)

Lights from sodium lamps ie. sodium vapour lights are omnidirectional. Omnidirectional lights produce light in 360 degrees. This is a large system inefficiency because at least half of the light needs to be reflected and redirected to the desired area being illuminated. Whereas LED lamps emit light directionally i.e. over 180 degrees which means there are far fewer losses from the need to redirect or reflect light. Hence, statement 1 is correct. LEDs have an extremely long lifespan relative to every other lighting technology (including sodium lamps). New LEDs can last 50,000 to 100,000 hours or more more than 3-4 times than sodium lamps. Hence, statement 2 is incorrect.

Sodium vapour lights have the worst colour rendering. Low pressure sodium lamps in particular are monochromatic resulting in the colours of illuminated objects being nearly indistinguishable, which means that the objects illuminated by them appear shadowy black rather than the colour you would see during daylight. LEDs waste much less energy producing waste heat and they also provide an incredibly better variety of high colour rendering index options to the user (thus eliminating the monochromatic black appearance of objects illuminated by sodium lamps). Hence, statement 3 is correct.

CFL uses mercury vapour and phosphor to produce light The gases becomes excited by electricity and when combined with mercury particles, produces invisible ultraviolet light. The UV light then hits the white phosphor coating inside the bulb causing it to fluorescence and emit white light. LED lamp uses semi-conductor material to produce light. CFLS have a life of about 6000 to 10,000 hours, while LED has a life span of about 50,000 hours. LED lamps are more energy efficient as compared to CFL.

Fluorescent lamps are filled with the low pressure gases specially Mercury and noble gases like Argon, Neon, Xenon and Krypton.

In comparison to electric bulb, fluorescent tubes transform more electric energy into light energy. A bulb of 100 watt converts only 5 percent of electric energy into light energy but fluorescent tubes convert approximately 22% of electric energy into light energy. Thus, none of the statement is true.

A tube light or fluorescent lamp is a kind of light that uses a combination of electricity and mercury vapour to create light energy. The electricity causes electrons to travel at high speed between the poles. These electrons hit the mercury gas molecules and oscillate them. The mercury gas is then ionized by the current flowing within, producing ultraviolet radiation. Since the human eye is unable to see this radiation, the glass tube is coated with a fluorescent material which changes it into white light. Thus, among the given options, option (d) is the correct answer

The electric bulb was invented by Edition. A coiled filament of tungsten metal with a high melting point fits inside it. To prevent the metal from oxidation,Nitrogen and Argon gases are filled in the bulb instead of vacuum.

Stater in tube lights increases the current and sends it to the choke. Choke coil steps up the voltage of the transmitted current and send it back to tubelight resulting tubelight to glow. After this work of the starter gets finished and choke is used to step up and step down  the voltage thus prevent the tubelight from any damage.

The transformer is used to step- up and step down the alternating current. There are two types of coils in transformer (i) Primary coil (2) Secondary coil. Alternating current flows through the primary coil which inflicts the potential in the secondary coil.

The transformer is used to step- up and step down the alternating current. There are two types of coils in transformer (i) Primary coil (2) Secondary coil. Alternating current flows through the primary coil which inflicts the potential in the secondary coil.

A mobile phone charger works on the simple principle of conversion of AC (alternating current) to DC (direct current). As we connected charger to 220 volt AC switchboard,the first job of the charger is to step down the  high 22 v in 9v or 10v. A step down transformer is used in mobile phone charger.