Olympiad Test: Chemical Effects Of Electric Current - Class 8 MCQ

Plastic wire is an insulator because it does not allow the flow of electric current. Insulators resist the flow of electricity, making them ideal for uses where electrical insulation is required.

• Insulators prevent the passage of electric current.
• They are essential for electrical insulation.
• Plastic wire is commonly used in various applications due to its insulating properties.

Electroplating is the process of coating an object with a thin layer of metal using an electric current. It primarily relies on the chemical effect of electricity. Here are the key points explaining this process:

• The process involves a solution containing metal ions.
• When an electric current is applied, metal ions are reduced and deposit onto the surface of the object.
• This method is widely used for decorative purposes and to enhance resistance to corrosion.
• Electroplating can improve the conductivity and durability of the coated item.

Overall, electroplating is an essential technique in various industries, providing both aesthetic and functional benefits.

Adding common salt to distilled water increases its conductivity.

When salt (sodium chloride) dissolves in water, it breaks down into sodium and chloride ions. This process enhances the solution's ability to conduct electricity. Here are some key points:

• Salt Dissolves: Sodium chloride dissociates into ions.
• Ion Movement: Ions carry electric charge through the solution.
• Improved Conductivity: The presence of ions makes the solution a good conductor.

In contrast, distilled water on its own is a weak conductor of electricity due to the absence of dissolved ions. Therefore, adding common salt transforms distilled water into a solution that conducts electricity effectively.

An electrolyte is a substance that can conduct electricity when dissolved in water or melted. It plays a crucial role in various chemical and biological processes. Here are some key points about electrolytes:

• They are typically ionic compounds that dissociate into ions in solution.
• Electrolytes are essential for maintaining fluid balance in the body.
• They help transmit electrical signals in nerves and muscles.
• Common examples include sodium chloride (table salt) and potassium ions.

In summary, an electrolyte is a liquid that can conduct electric current due to the movement of ions. This property is vital for functions such as nerve impulses and muscle contractions.

Copper wire is known for its excellent conductivity, making it a popular choice in electrical applications. Here are some key points about copper wire:

• Good Conductor: Copper is one of the best conductors of electricity, allowing electric current to flow easily.
• Durability: Copper wire is resistant to corrosion and can withstand various environmental conditions.
• Flexibility: It can be easily bent and shaped, which is ideal for various installations.
• Cost-Effective: While there are alternatives, copper remains a cost-effective solution for many electrical needs.

In summary, copper wire is a highly efficient and reliable choice for electrical wiring due to its strong conductive properties and other advantageous characteristics.

Poor conductors of electricity are materials that do not allow electrical current to pass through them easily. Here are some common examples:

• Plastics - These materials are widely used for insulation and are poor at conducting electricity.
• Clothes - Most fabrics do not conduct electricity well, making them safe to wear.
• Wood - Dry wood is also a poor conductor, which is why it is often used in electrical applications.

In summary, all of these materials—plastics, clothes, and wood—are considered to be poor conductors of electricity.

Distilled water is a poor conductor  of electricity because it doesn't contain any dissolved salts in it which can provide it ions to conduct electricity.

Electricity is a term used to describe the energy produced (usually to perform work) when electrons are caused to directional (not randomly) flow from atom to atom. In fact, the day-to-day products that we all benefit from, rely on the movement of electrons. This movement of electrons between atoms is called electrical current. 

Electroplating is a process that provides several protective benefits, primarily aimed at enhancing the durability of metal objects. This method involves coating a metal surface with a thin layer of another metal, which serves to:

• Prevent rusting: By creating a barrier, electroplating protects the underlying metal from moisture and air, which are the main causes of rust.
• Enhance appearance: The layer of metal can improve the visual appeal, giving a shiny, polished look to the object.
• Increase corrosion resistance: Certain metals used in electroplating are less prone to corrosion, further extending the life of the base metal.
• Improve conductivity: In some cases, electroplating can enhance the electrical conductivity of the surface, which is vital for various electronic applications.

Overall, electroplating is an effective technique to protect metal items from degradation, ensuring they remain functional and aesthetically pleasing over time.

Plastics are not good conductors of electricity.

In general, plastics are considered insulators, meaning they do not conduct electricity well. Here's a clearer breakdown:

• Conductors are materials that allow electric current to flow easily, like metals.
• Insulators resist the flow of electricity, making them ideal for protecting against electric shocks.
• Most plastics have high electrical resistance, which is why they are used to coat wires and electrical components.
• However, certain types of plastics can be engineered to conduct electricity, but these are exceptions rather than the rule.

Therefore, it is accurate to say that plastics are generally poor conductors of electricity.

The flow of electrons is known as electric current. Here are some key points to understand this concept:

• Electric current is the movement of charged particles, primarily electrons, through a conductor.
• This flow generates an electric field and can produce various effects, such as heating and magnetic fields.
• Current is measured in amperes (A), which indicates the quantity of electrons flowing per second.
• There are two types of electric current: direct current (DC) and alternating current (AC).

Understanding electric current is fundamental in the field of electrical engineering and many everyday applications, such as powering devices and lighting.

The correct option is A.
circuit A path through which electric charges flow. A continuous, unbroken path through which electrons can flow is a closed circuit. Charges, or current, can flow only through a closed circuit. A break or opening in a circuit creates an open circuit.

The electric bulb has a filament called tungsten when electricity passes through this filament, it heats up and glows. This heat is generated due to the passage of electric current and the drift of electrons due to the current and the resistance it causes.
Hence, the glowing of electric bulb is based on the heating effect of electric current.

Copper wire is a poor conductor of electricity.

This statement is false. Here’s why:

• Copper is widely recognised as one of the best conductors of electricity.
• It has a low electrical resistance, which allows electric current to flow easily.
• Due to its excellent conductivity, copper is commonly used in electrical wiring.
• Alternative materials, like aluminium, are often less efficient than copper.

In summary, copper wire is not a poor conductor; rather, it is one of the most effective materials for conducting electricity.

LEDs (Light Emitting Diodes) are commonly used in electrical testing devices.

• LEDs are efficient and provide a reliable indication of current flow.
• They function by emitting light when an electric current passes through them.
• LEDs are durable and have a long lifespan compared to traditional bulbs.

In a tester, the LED lights up to show that the device is operational and that current is present.

If you run an electric current through a metal object, it exhibits magnetic behavior. However, simply passing current through iron doesn't make it magnetic. Yet, if you direct current through a coil wound around iron, it becomes magnetized. Even without iron in the coil, passing direct current through it generates a magnetic field akin to a magnet. Similarly, directing current through a coil around bismuth creates a magnet-like magnetic field.
 Electricity shows magnetic effect is true.

When salt is dissolved in distilled water, it does not conduct electricity.

When salt (sodium chloride) is added to distilled water, it actually does conduct electricity. This is because:

• Dissociation: Salt molecules break apart into ions (sodium and chloride).
• Ion Mobility: These ions are charged particles that can move freely in water.
• Electrical Conductivity: The movement of ions allows the solution to conduct electricity.

In contrast, distilled water itself is a poor conductor of electricity due to the lack of ions. Therefore, when salt is added, the conductivity increases significantly.

The process of depositing a thin layer of a desired metal over a metal object with the help of electric current is called electroplating. So, Electroplating is based on chemical effect of electricity.