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Class-8-Science-Chemical Effect of Electric Current

Electricity CBSE Class-8
Q1: What do you mean by chemical effect of current?

Answer: When an electric current passes through a conducting solution, chemical reactions take place in the solution. This is called the chemical effect of electric current.

Q2: What are good conductors?

Answer: Objects which allow current to pass through it are called good conductor.

Q3: What are insulators or poor conductors?

Answer: Objects which don't allow current to pass through it are called good conductor.

Q4: Give four examples of conductors.

Answer: four example of conductor are:- Iron, copper, silver, gold

Q5: Name two metal objects which have a coating of another metal.

Answer: Bathroom taps, bicycle handle

Q6: What do we get on electrolysis of acidified water?

Answer: Hydrogen(H2+), oxygen(O2-) are separted form water when electrolysed

Q7: Which metal is plated on handle bars of cycles and rim of wheels?

Answer: Chromium

Q8: What is the full form of LED?

Answer: Light Emitting Diode

Q9: How do we check the electric current?

Answer: To check whether a electric current is being passed through an object by galvenometer or volt meter or tester.

Q10: Which of these will conduct electricity- tap water or distilled water? Why?

Answer: Tap water will conduct electricity because tap water contains salts dissolved in it. When electricity passes through tap water, the salts dissociate into cations and anions.They behaves like a charge carrier and conduct electricity through the tap water. Whereas distilled water does not contain any kind dissolved salts. When electricity is passed through it, there are no charge carriers present in it, hence distilled water does not conduct electricity.

Q11: Conduction of electricity in liquids occurs through electrons. Do you agree? Give reasons.

Answer: No, conduction of electricity in liquids occur due to ions. These ions are responsible for electric current in liqiuids when there is a potencial diffrence.

Q12: What are ions?

Answer: They are chemical species which holds a positive or negative charge of some magnitude. there are two types of ions :- Cations(+ve), Anions(-ve).

Q13: Does pure water conduct electricity? If not. what can we do to make it conducting?

Answer: No, pure water doesn't conduct electricity as it does not have any free ions and impurites. To make it conducting we can add a pinch of salt.

Q14: Explin the process of electroplatig.


  • STEP 1:- Take any metal like copper. It should be in a form of sheet. Add it to the positivee terminal(anode) and thing to electroplated at the negative terminal(cathode.)
  • STEP 2:- In the beaker add copper sulphate solution (CuSO4).
  • STEP 3:- Allow the electric current to pass through it for 15 minutes.
  • STEP 4:- IN the 15 minutes the copper went upon the negative terminal because when electricity is passed through copper sulaphate solution then it deposited into copper and sulphate. The free copper gets drawn to the negative terminal of the battery. Hence it gets deposited on the object.

Q15: What happens when electricity is passed through a potato.

Answer: When electricity is passed through a potato then there a greensih-blue spot o the positive teminal.

Q16: If the bulb doesn't glow what are the possible reasons.


  • That the cell is used up.
  • The bulb's fused.
  • The connection is loose somewhere.
  • The bulb needs more energy to glow.
  • The liquids is not a good conductor.

Q17: Explain the process of electrolysis.


  • STEP 1:- Take a glass of water and add any acid, base, salt to it.
  • STEP 2:- Take two carbon rods and connect it to the tester. and remove the bubln or the LED.
  • STEP 3:- Pass electricity to it.
  • STEP 4:- You will observe that bubles of Hydrogen(H2+), oxygen(O2-) are formed at positive and negative terminal.
  • STEP 5:- At cathode the bubles will be more as Hydrogen is double then oxygen. At anode the bubles will be less as oxygen is less then hydrogen in water.

Q18: Name the person who discovered electrolysis of water.

Answer: In 1800, William Micholson had show electrolysis of water for the first time.

Q19: Why is a layer of zinc coated over iron?

Answer: If iron is left in mositure for much long it goes under rusting. To prevent it from corrosion a process named galvanistaion is performed, zinc is electroplated on iron.

Q20: Why is tin electroplated on iron to make cans used for storing food?

Answer: Tin is highly reactive and can spoil the food item so tin is electroplated on iron for making cans.

Q21: What is the major concern for electrplating factories?

Answer: In the electroplating factories the disposal of the used conducting solution is a major concern. It is a polluting waste and there are specific disposal guidlines to protect th environment.

Q22: What is the defination of electroplating and electrolysis?


  • Electrplating:- The process of depositing any desired metal uopn another metal by help of electricity is called electroplating.
  • Electrolysis:- The process of separating hygrogen and oxygen from water by the means of electricity is called electrolysis.

Q23: What is a gavlenometer?

Answer: A device used to check current passes through object is called gavlenometer.

Q24: A child staying in a coastal region test the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you ex¬plain the reason?

Answer: Seawater contain more salt then drinking water, hence sea waater is a good conductor of electricity and it has stronger magentic feild and that's why compass deflects more i the case of seawater.

Q25: A liquid which conduct electricity is called _______.

Answer: electrolyte.

Q26: A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.

Answer: (i) liquid A is a better conductor than liquid B.

Q27: When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Answer:We know when electric current flows through any object it creates magnetic feild around it. In the similar way when the free ends of a tester are dipped into a solution, then the circuit is complete and shows deflection of needle in the compass. It also shows that liquid conduct electricity.

Q28: In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

Answer: The water used in the water hoses is not pure water and is a good conductor of electricity. So, the fire¬men shut off the electric supply before spraying water to save themselves and other people from electrocution.


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