Electricity

61.Why is air completely removed from an electric bulb?
 
A. To prevent oxidation of tungsten filament
 
B. To prevent the bulb from exploding
 
C. To prevent loss of light due to absorption
 
D. None of the above
 
Option “A” is correct.
In summary, bulbs on Earth have most of the air removed or are simply filled with an inert gas (one that does not burn or aid combustion) in order to keep oxygen away from a light bulb’s filament. Thus the globe is necessary to keep the filament isolated from the oxygen in the Earth’s atmosphere.
62.Fluorescent tube is preferred over electric bulb because-
 
A. It has a larger light-emitting surface
 
B. Voltage fluctuations do not affect it
 
C. In a tube, electrical energy is almost converted into light
 
D. None of these
 
Option “C” is correct.
In a fluorescent tube, electrical energy is almost converted into light.
The inner wall of the fluorescent tube is coated with phosphorus which immediately transformed into bright light.
63.What is the difference between CFL and LED lamp
 
A. CFL uses mercury vapor and irradiant to produce light while LED lamp uses semiconductor materials.
 
B. Average life span of CFL is much higher than LED lamp
 
C. CFL is less energy efficient as compared to LED lamp
 
D. 1 OR 3 OPTIONS
 
Option”D” is correct.

  • Difference between the CFL and LED bulb:
    • The primary difference between the CFL and LED bulb is that LED bulbs are more durable and has a long life. Hence, statement 2 is incorrect.
    • LED bulb consumes less power as compared to CFL.
    • LED bulbs are expensive as compared to CFL bulbs.
    • LED bulbs are much more efficient than CFL bulbs. Hence, statement 3 is correct.
  • CFL bulbs are made up of argon and mercury in small quantities. 
    • In a CFL, an electric current is driven through a glass tube containing argon and a small amount of mercury vapour. This generates invisible ultraviolet light that excites a fluorescent coating (called phosphor) on the inside of the tube, which then emits visible light.
  • The main semiconductor materials used to manufacture LEDs are:
    • Indium gallium nitride (InGaN): blue, green, and ultraviolet high-brightness LEDs.
    • Aluminium gallium indium phosphide (AlGaInP): yellow, orange, and red high-brightness LEDs.
    • Aluminium gallium arsenide (AlGaAs): red and infrared LEDs. 

64.Nichrome wire is commonly used in heating elements because of its
 
A. Low specific resistance
 
B. Low melting point
 
C. High specific resistance
 
D. High conductivity
 
Option “C” is correct.
Due to high specific resistance of Nichrome, the resistance of a nichrome wire of a finite length is high. Hence when a particular amount of current is passed through the wire, the power of heating, I^2R, has a large value and hence it heats more quickly as compared to other materials.
65.A tube light converts ___.
 
A. electrical energy to light energy
 
B. light energy to electrical energy
 
C. electrical energy to mechanical energy
 
D. mechanical energy to electrical energy
 
Option “A” is correct.
A tube light is an electrical device used to produce light. It converts electrical energy to light energy.
66.The domestic appliance based on the heating effect of electric current is__
 
A. Electric heater
 
B. Electric heater
 
C. Electric geyser
 
D. All of the above
 
Option “D” is correct.
Domestic appliances based on the heating effect of electric current:
1) Electric Iron
2) Electric heater
3) Electric geyser
4) Induction Cooker
5) Microwave Oven
6) Hair blower
67.A 100 W electric bulb is used for 10 hours a day. How many units of energy are consumed in 30 days?
 
A. 1 unit
 
B. 0.1 units
 
C. 10 units
 
D. 30 units
 
Option “D” is correct.

It is given that,

Power Rating of the bulb = 100 W

Duration for which the bulb is used = 10 hours a day

Number of Days = 30 days

Total Energy Consumed by the Electric Bulb = Power × Duration

= 100 W × 10 hrs/day × 30 days

= 30,000 W-hrs

= 30 kWh is the unit of energy consumed.

68.A 100 watt electric bulb is used for 10 hours. What will be the cost of electricity consumed, if the consumption cost is ₹ 5 per unit ?
 
A. 5 Rs.
 
B. 10 Rs.
 
C. 25Rs.
 
D. 50 Rs.
 
Option”A” is correct.
The cost of electricity will be ₹ 5.
1 unit of electricity
= 1 kwh (1 kilowatt hour)
= 100/1000 kilowatt x 10 hour
= 1 unit hence electricity bill
= 1 x 5 = ₹ 5
69.Kilowatt hour is the unit of
 
A. Potential difference
 
B. Electric power
 
C. Electrical energy
 
D. Electrical potential
 
Option “C” is correct
70.Whose measurement is the electricity consumption bill based on? 1. Wattage 2. Voltage 3. Ohm ampere Select the correct answer from the codes given below –
 
A. only 1
 
B. 1 and 2
 
C. 2 and 3
 
D. 1 and 4
 
Option”A” is correct.
The power consumption of small devices is usually measured in Watts, and the power consumption of larger devices is measured in kilowatts (kW), or 1,000 Watts. Electricity generation capacity is often measured in multiples of kilowatts, such as megawatts (MW) and gigawatts (GW).

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