Electricity

21.Mica is __
 
A. Bad conductor of heat and electricity
 
B. Conductor of both heat and electricity
 
C. Poor conductor of heat and conductor of electricity
 
D. Conductor of heat and bad conductor of electricity
 
Option “A” is correct.
Mica can be made into thin sheets. They are heat tolerant, insulating and dielectric. Because of these properties, they are used in electrical appliances. They are used in control devices, heating devices, neon lights and other lighting equipment.
22.The temperature of the filament of lighted electric bulb is generally
 
A. 1000-500°C
 
B. 1000°C-1500°C
 
C. 2000°C-2700°C
 
D. 30000-3500°C
 
Option “C” is correct
23.Ampere is a unit of _________.
 
A. Voltage
 
B. Electric current
 
C. Resistance
 
D. Power
 
Option “B” is correct.

  • Ampere is the SI unit of Electic current.
  • The International System of Units defines the ampere in terms of other base units by measuring the electromagnetic force between electrical conductors carrying electric current.
  • It is named after André-Marie Ampère (1775–1836), a French mathematician and physicist, considered the father of electromagnetism.
  • In SI, the unit of charge, the coulomb, is defined as the charge carried by one ampere during one second.

24.The source of electrical energy in an artificial satellite is
 
A. Small nuclear reactor
 
B. Solar energy
 
C. Thermometer
 
D. None of these
 
Option “B” is correct.

  1. The artificial satellites contain solar panels.
  2. Solar panels harness the solar energy of the Sun.
  3. The light energy incident on the solar panels is converted into electrical energy.
  4. This electrical energy is used in artificial satellites.
  5. This solar energy is a vital source of electric needs for artificial satellites.

Hence, solar energy is the main source of electric needs for artificial satellites.

25.The device for converting electrical energy into mechanical energy is
 
A. Dynamo
 
B. Transformer
 
C. Electric motor
 
D. Inductor
 
Option “C” is correct.
The most common device for changing electrical energy into mechanical energy is the motor. Most motors use electromagnets to cause mechanical rotation, which can do work.
26.Which of the following converts chemical energy into electrical energy?
 
A. Electric fuse
 
B. Dry cell
 
C. Electric cooker
 
D. LED
 
Option “B” is correct.
An electric fuse protects the home appliances from large currents and there is no conversion of energy taking place in it. An LED converts electrical energy into light energy. A dry cell converts chemical energy into electrical energy. An electric cooker converts electrical energy into heat energy.
27.The semiconductor chip used in an integrated circuit is made up of__
 
A. Calcium
 
B. Carbon
 
C. Silicon
 
D. Zircon
 
Option “C” is correct.
Most ICs are made of silicon, which is abundant in ordinary beach sand. Pure crystalline silicon, as with other semiconducting materials, has a very high resistance to electrical current at normal room temperature.
28.The device that converts alternating current to direct current is called__
 
A. Inverter
 
B. Rectifier
 
C. Transformer
 
D. Transmitter
 
Option “B” is correct.
The device that is used to convert AC to DC is a rectifier. As the name suggests, a rectifier corrects or straightens the direction of the current. This device periodically reverses the direction of alternating current (AC) to direct current (DC), which usually flows in just one direction.
29.Transformers are used-
 
A. To convert AC to DC
 
B. To convert DC to AC
 
C. To substract DC voltage
 
D. To generate or reduce AC voltage
 
Option “D” is correct.
Transformers are used in AC circuits to step up or step down voltage. In DC circuits, since the current is constant, induction cannot happen.
30.The most commonly used material in fluorescent tubes is
 
A. Sodium oxide
 
B. Sodium vapor and neon
 
C. Mercury vapor and argon
 
D. Mercuric oxide and neon
 
Option “C” is correct.
Mercury vapour and argon are the most commonly used substance in fluorescent tubes.

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