CBSE Class 8 Science – MCQ and Online Tests – Unit 14 – Chemical Effects of Electric Current
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CBSE Class 8 Science – MCQ and Online Tests – Unit 14 – Chemical Effects of Electric Current
Choose the correct option.
Question 1.
An electric lamp glows due to
(a) heating effect
(b) magnetic effect
(c) chemical effect
(d) physical effect
Answer
Answer: (a) heating effect
Question 2.
Electroplating prevents
(a) corrosion
(b) passing of current
(c) dissociation
(d) shining
Answer
Answer: (a) corrosion
Question 3.
An electric current can produce
(a) heating effect
(b) chemical effect
(c) magnetic effect
(d) all of these
Answer
Answer: (d) all of these
Question 4.
Pure or distilled water is a
(a) poor conductor
(b) good conductor
(c) both (a) and (b)
(d) none of these
Answer
Answer: (a) poor conductor
Question 5.
Which of the following is a good conductor?
(a) Brick
(b) Steel
(c) Plastic
(d) Cotton
Answer
Answer: (b) Steel
Question 6.
Polythene is
(a) a conductor
(b) an insulator
(c) both (a) and (b)
(d) none of these
Answer
Answer: (b) an insulator
Question 7.
Electroplating is based on
(a) heating effect of electricity
(b) chemical effect of electricity
(c) physical effect of electricity
(d) magnetic effect of electricity
Answer
Answer: (b) chemical effect of electricity
Question 8.
Copper is
(a) a good conductor
(b) an insulator
(c) both (a) and (b)
(d) none of these
Answer
Answer: (a) a good conductor
Question 9.
Waste from an electroplating factory must be disposed off
(a) in the nearby river
(b) in the nearby pond
(c) in the nearby cornfield
(d) according to the disposal guidelines of Waste Management Bodies
Answer
Answer: (d) according to the disposal guidelines of Waste Management Bodies
Question 10.
An electrolyte is
(a) a metal
(b) a liquid that conducts current
(c) a non-metal
(d) none of these
Answer
Answer: (b) a liquid that conducts current
Question 11.
Which of the following is a bad conductor of electricity?
(a) Distilled water
(b) Silver nitrate
(c) Sulphuric acid
(d) Copper sulphate
Answer
Answer: (a) Distilled water
Question 12.
Which of the following does not conduct electricity?
(a) Sugar solution
(b) Vinegar solution
(c) Lemon juice solution
(d) Caustic soda solution
Answer
Answer: (a) Sugar solution
Question 13.
Which is not a non-electrolyte?
(a) Ethyl alcohol
(b) Sodium chloride
(c) Urea
(d) Sodium solution
Answer
Answer: (b) Sodium chloride
Question 14.
The process of depositing a layer of any desired metal on another material by means of electricity is called ___________.
(a) Electric plating
(b) Electroplating
(c) Electric depositing
(d) None of the above
Answer
Answer: (b) Electroplating
Question 15.
Some liquids are good conductors of electricity and some are poor conductors. Which one is a poor conductor?
(a) Acidic solution
(b) Alkaline solution
(c) Common Salt solution
(d) Distilled water
Answer
Answer: (d) Distilled water
Question 16.
Which of the following is not used for electroplating metal articles?
(a) Nickel
(b) Silver
(c) Chromium
(d) Sodium
Answer
Answer: (d) Sodium
Question 17.
Iron objects can be protected by electroplating them with
(a) chromium
(b) nickel
(c) zinc
(d) all of these
Answer
Answer: (d) all of these
Question 18.
In LEDs, the longer lead (wire) is always connected to the _______ terminal
(a) negative
(b) neutral
(c) positive
(d) Any terminal
Answer
Answer: (c) positive
Question 19.
Chromium plating is done on many objects such as car parts, bath taps, kitchen gas stove etc. Why?
(a) It does not corrode but prevents scratches
(b) It looks beautiful
(c) It costs less
(d) Articles can be sold at higher price
Answer
Answer: (a) It does not corrode but prevents scratches
Question 20.
Tap water is a good conductor of electricity while distilled water is not because
(a) Tap water contain salts
(b) Distilled water do not contain salt
(c) Only (a) is correct
(d) Both (a) & (b) is correct
Answer
Answer: (b) Distilled water do not contain salt
Question 21.
When electrodes are immersed in water and electricity passed, the bubbles formed on the positive terminal is actually _______ gas.
(a) Hydrogen
(b) Carbon dioxide
(c) Oxygen
(d) Nitrogen
Answer
Answer: (c) Oxygen
Question 22.
When electrodes are immersed in water and electricity passed, the bubbles formed on the negative terminal is actually _______ gas.
(a) Hydrogen
(b) Carbon dioxide
(c) Oxygen
(d) Nitrogen
Answer
Answer: (a) Hydrogen
Question 23.
Why do we add little dilute sulphuric acid to copper sulphate solution during electroplating?
(a) To increase acidity
(b) To increase conductivity
(c) So that the colour becomes more prominent
(d) To burn copper sulphate
Answer
Answer: (b) To increase conductivity
Question 24.
A coating of _________is deposited on iron to protect it from corrosion and formation of rust
(a) copper
(b) aluminium
(c) Zinc
(d) silver
Answer
Answer: (c) Zinc
Question 25.
Flow of electron is called
(a) electrolyte
(b) electroplating
(c) electrodes
(d) electric current
Answer
Answer: (d) electric current
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