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NCERT 8th Class (CBSE) Science: Chemical Effects of Electric Current

Question: What is electric current?

Answer: The flow of electrons constitutes an electric current.

Question: How is electronic current different from conventional current?

Answer: The flow of electronic current is from negative to positive whereas the flow of conventional current is from positive to negative.

Question: Differentiate between conductors and insulators.

Answer: Difference is as follows:

Conductors
Insulators
1. Substances which allow electric charges to flow through them are called conductors of electricity.
1. Substances that do not allow electric charges to flow through them are called non-conductors or insulators of electricity.
2. Examples: Metals like iron, copper, aluminium, etc. 
2. Examples: Plastic, rubber, wood, etc.

Question: What is an electrolyte?

Answer: A substance which conducts electricity in the liquid state or when dissolved in water and breaks up chemically during the process is called an electrolyte.

Question: Why is zinc electroplated on iron?

Answer: Zinc is electroplated on iron to prevent it from rusting.

Question: Draw a circuit diagram showing a dry cell connected to a bulb through a switch. Mark the positive and the negative terminals of the cell, and the direction of flow of a. electron, b. conventional current.

Answer:

Circuit diagram showing a dry cell connected to a bulb
Circuit diagram showing a dry cell connected to a bulb

 

Question: What are the advantages of electroplating iron with chromium?

Answer: Chromium is a shiny metal that does not corrode and resists scratches. It makes iron look more attractive and also resist corrosion.

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