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Chemical Effects of Electric Current

Bicycle handle bars are usually

a) Tin plated.
b) Chromium plated.
c) Zinc plated.
d) Gold plated.

✔Answer

✔Solution

Correct Answer Is : Chromium plated.

Solution Is : Car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims etc., made of iron are coated with chromium, as it does not corrode and can also resist scratches.

The decomposition of an electrolyte, by passing electricity through it is called

a) Electroplating.
b) Electrolysis.
c) Conduction.
d) Convection.

✔Answer

✔Solution

Correct Answer Is : Electrolysis.

Solution Is : When electricity is passed through an electrolyte, it dissociates into positive and negative ions.This process is called electrolysis.

The electrical process of coating an inexpensive conductor with an expensive metal is called

a) Electroplating.
b) Electro-refining.
c) Conduction.
d) Coating.

✔Answer

✔Solution

Correct Answer Is : Electroplating.

Solution Is : Electroplating is the process of deposition of a layer of one metal over another metal, by passing electric current through conducting liquids.Using this process, an inexpensive conductor is coated with an expensive metal.

Metals can be extracted from their ores by the method of

a) Electroplating.
b) Electrolysis.
c) Conduction.
d) Mining.

✔Answer

✔Solution

Correct Answer Is : Electrolysis.

Solution Is : Electrolysis is the chemical process by which a compound in its molten state is decomposed into its elements.So, electrolysis is used for the extraction of metals from their naturally-occurring sources, such as ores etc.

In order to refine certain metals, such as copper and zinc we use

a) Electroplating.
b) Electrolysis.
c) Conduction.
d) Coating.

✔Answer

✔Solution

Correct Answer Is : Electrolysis.

Solution Is : Electrolysis is used for purifying a metal from an impure sample of the metal.An electric current is passed between a sample of the impure metal and a cathode when both are immersed in the metal solution.The metal is stripped off the impure sample and deposited in pure form on the cathode.

When the switch is in the OFF position,

a) The positive terminal of the battery is joined to the negative terminal.
b) The circuit is said to be closed.
c) The current flows throughout the circuit instantaneously.
d) The circuit is said to be open.

✔Answer

✔Solution

Correct Answer Is : The circuit is said to be open.

Solution Is : When the switch is in the `ON` position, the circuit is continuous without any breaking points and the circuit is said to be closed.Current flows in such circuit.When it is in `OFF` position, it is called open circuit as the circuit is discontinuous with breaking points and no current flows.

The thin wire that glows when current passes through a bulb is made up of

a) Tungsten.
b) Tin-lead alloy..
c) Lead.
d) Cadmium.

✔Answer

✔Solution

Correct Answer Is : Tungsten.

Solution Is : When electric current is made to pass through a conductor (e.g.wire), it gets heated up due to `heating effect of electric current`.The temperature of heat produced is ot sufficient enough to melt tungsten as it has very high melting point but others will melt.

The bulb gets fused when

a) It becomes milky.
b) The filament breaks.
c) The glass breaks.
d) The bulb becomes too old.

✔Answer

✔Solution

Correct Answer Is : The filament breaks.

Solution Is : When electric current passes through a wire, it gets heated due to the heating effect of electric current.Sometimes, due to a short circuit or overload, the current becomes so strong that the heat produced melts the filament of the bulb, leading the bulb to fuse.

It is safe

a) To touch a lighted electric bulb.
b) To carry experiments with electric supply from the mains.
c) To use electric cells for experiments.
d) To carry experiments with electric supply off

✔Answer

✔Solution

Correct Answer Is : To carry experiments with electric supply off

Solution Is : It is unsafe to touch a lighted electric bulb because it is hot.One should not carry experiments with electric supply from the mains as it may give electric shocks.

When an electric current passes through a wire, it

a) Breaks.
b) Elongates.
c) Becomes hot.
d) Becomes cold.

✔Answer

✔Solution

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Class 8 Science Study Material

Chemical Effects of Electric Current

Bicycle handle bars are usually

Correct Answer Is : Chromium plated.

Solution Is : Car parts, bath taps, kitchen gas burners, bicycle handlebars, wheel rims etc., made of iron are coated with chromium, as it does not corrode and can also resist scratches.

The decomposition of an electrolyte, by passing electricity through it is called

Correct Answer Is : Electrolysis.

Solution Is : When electricity is passed through an electrolyte, it dissociates into positive and negative ions.This process is called electrolysis.

The electrical process of coating an inexpensive conductor with an expensive metal is called

Correct Answer Is : Electroplating.

Solution Is : Electroplating is the process of deposition of a layer of one metal over another metal, by passing electric current through conducting liquids.Using this process, an inexpensive conductor is coated with an expensive metal.

Metals can be extracted from their ores by the method of

Correct Answer Is : Electrolysis.

Solution Is : Electrolysis is the chemical process by which a compound in its molten state is decomposed into its elements.So, electrolysis is used for the extraction of metals from their naturally-occurring sources, such as ores etc.

In order to refine certain metals, such as copper and zinc we use

Correct Answer Is : Electrolysis.

When the switch is in the OFF position,

Correct Answer Is : The circuit is said to be open.

The thin wire that glows when current passes through a bulb is made up of

Correct Answer Is : Tungsten.

Solution Is : When electric current is made to pass through a conductor (e.g.wire), it gets heated up due to `heating effect of electric current`.The temperature of heat produced is ot sufficient enough to melt tungsten as it has very high melting point but others will melt.

The bulb gets fused when

Correct Answer Is : The filament breaks.

Solution Is : When electric current passes through a wire, it gets heated due to the heating effect of electric current.Sometimes, due to a short circuit or overload, the current becomes so strong that the heat produced melts the filament of the bulb, leading the bulb to fuse.

It is safe

Correct Answer Is : To carry experiments with electric supply off

Solution Is : It is unsafe to touch a lighted electric bulb because it is hot.One should not carry experiments with electric supply from the mains as it may give electric shocks.

When an electric current passes through a wire, it

Correct Answer Is : Becomes hot.

Solution Is : A wire gets hot due to the heating effect of electricity, when an electric current passes through it.

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