Electricity

91.The thick and long pin in a three pin plug is connected to __.
 
A. live wire
 
B. earth wire
 
C. neutral wire
 
D. either live or earth wire
 
Option “B” is correct.
The pin which is long and thick in a three pin plug is the earth pin. It ensures safety against electric shock.
It is made thick to avoid inserting it into the live wire socket by mistake. Also, it is made long to ensure that it is always connected prior to the connection of live wire.
92.Of the two bulbs in a house, one glows brighter than the other. Which of the two has a large resistance?
 
A. The bright bulb
 
B. The dim bulb
 
C. Both have the same resistance
 
D. The brightness does not depend upon the resistance
 
Option “B” is correct.
All home appliances are connected in parallel combination so they get equal voltage always. hence if two bulb are in some house and one glows brighter and other very dim it directly depends upon power of bulb i.e. energy emitted by bulb per unit second. power directly depends upon resistance of bulb.

Hence brighter bulb has more emitted power hence less resistance and dimmer bulb has low power hence larger resistance
93.The value of one kilowatt hour is
 
A. 3.6 x10⁶ joules
 
B. 3.6 x 10³
 
C. 10 July
 
D. 10 July
 
Option”A” is correct.
Kilo-watt hour is a unit of energy used to denote the energy consumption of large machinery and the electricity consumption in homes and industries. It is also a common unit representation in electrical power engineering. So, one 1KWh contains 3.6×106 Joules.
94.What is the purpose of choke in fluorescent lamp?
 
A. Reduce the flow of current
 
B. Increase the flow of current
 
C. Reduce resistance
 
D. Momentary voltage drop
 
Option “A” is correct.
The choke primarily serves to limit current flow to the correct level for the tube. It also can be used during startup to provide an inductive ‘kick’ forming a momentary higher-voltage pulse to start the lamp.
95.The electrical resistance of a conductor is independent of
 
A. Size of conductor
 
B. Temperature of conductor
 
C. Geometry of conductor
 
D. All of these
 
Option “D” is correct.
The electrical resistance of a conductor is depend upon all factors i.e., size, temperature and geometry of conductor.
96.If the electrical resistance of a typical substance falls to zero, then what is that substance called?
 
A. Superconductor
 
B. Semi-conductor
 
C. Conductor
 
D. Insulator
 
Option “A” is correct.

  • Current flows in the opposite direction in which free electrons flows in a substance. This phenomenon is known as the current electricity.
  • A substance can be divided into the four types based on their conductivity of the electricity or you can say based on their free electron number present on their surface:
  • Insulator: The substances that do not allow the current to flow through them. They don’t have any free electrons.
    example. – Cotton, Wood, Glass, etc.
  • Conductors: The substances that allows the current to flow through them are known as conductors. They have a large number of free electrons.
    eg:- Copper, Silver, Iron, Aluminum, etc.
  • Superconductors: This substance that has zero resistance at a very low temperature. so electricity flows through them rapidly.
    eg- Mercury below 4.2 K, lead below 7.25 K are act like superconductors. (K= kelvin)
  • Semiconductors: Some substances that have electrical resistivity between those of conductors and insulators.
    eg.- Silicon and germanium.

97.If a resistive wire is lengthened, then its resistance-
 
A. Increases
 
B. Decreases
 
C. Remains constant
 
D. All of the above
 
Option “A” is correct.

The length of the wire is directly proportional to the resistance. The longer the wire, greater it’s resistance. The longer the wire is, more number of collisions occur while the electrons travel from one end of the wire to another. This increases the resistance.
98.Electricity remains in mercury lamp in which mercury is at __
 
A. at low pressure
 
B. at high pressure
 
C. at no pressure
 
D. None of these
 
Option “A” is correct.
What is a low pressure mercury lamp?
Image result for Electricity remains in mercury lamp mercury at low pressure
The low-pressure mercury lamp is a discharge lamp designed to have a low mercury vapor pressure (100 Pa max.) when lit to efficiently emit the mercury resonance lines (254 nm or 185 nm). The figure here shows the spectral distribution of a low-pressure mercury lamp.
99.The device used to change the speed of an electric fan is
 
A. Amplifier
 
B. Regulator
 
C. Switch
 
D. Rectifier
 
Option “B” is correct
100.MCB which disconnects the power supply in case of short circuit works
 
A. chemical effect of current
 
B. heating effect of current
 
C. magnetic effect of current
 
D. electroplating effect of current
 
Option “C” is correct.
MCB(miniature circuit breaker) contains an electromagnet. When the current increases heavily, the electromagnet become strong to separate the pair of contacts and break the circuit.
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