Important Questions: Chemical Effects of Electric Current - Class 8 MCQ

The correct answer is: D: Rate of flow of electrons.

In an electrolyte, the movement of charge carriers is essential for conducting electricity. Let's break down the roles of different particles in this context

1. Understanding Electrolytes: Electrolytes are substances that dissociate into ions when dissolved in a solvent, typically water. This dissociation allows the solution to conduct electricity
2. Identifying Charge Carriers: The charge carriers in an electrolyte are primarily ions. Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a net electrical charge
3. Role of Different Particles

• Electrons: While electrons are charge carriers in metallic conductors, they do not move freely in electrolytic solutions
• Protons: Protons are positively charged but are not mobile in solutions; they are found in the nucleus of atoms
• Neutrons: Neutrons are neutral particles and do not carry any charge, hence they cannot act as charge carriers
• Ions: Ions, which can be either positively charged (cations) or negatively charged (anions), are the primary carriers of charge in electrolytes. Their movement allows for the flow of electric current through the solution

Therefore, in an electrolyte, the correct answer is that ions act as the carriers of charge

The correct answer is Wood.

Key Points

Insulator:

• The insulator is a material that resists the flow of current.
• It also doesn't allow the flow of heat to pass through them.
• It doesn't have free electrons that the reason for its non-conducting nature.
• They have high resistivity.
• Insulators are protectors.
• Example: Glass (highest resistivity), wood, rubber, clothes, mica, quartz.
• Applications:
  • Thermal Insulators: Resist the follow of heat. So we can use it in thermoplastic bottles, ceiling and roofs. 
  • Electrical Insulators: Resist the follow of current. So we can use it in an electrical circuit, cables, high voltage system, safety equipment.
  • Sound Insulators: Hinder the sounds and easily absorbs them. So we can use it in the conference hall, buildings.

Important Points

Conductor:

• The conductor is a material that allows the flow of current through them.
• It also allows the flow of heat to pass through them.
• They conduct electricity because they allow the electron to pass through them. 
• They also have free electron on their surface which allow electricity to pass through them.
• Example: Metals (Silver is the best conductor of electricity), humans, animals, Earth. 

An LED has two leads. One lead is slightly longer than the other. The longer lead is always connected to a positive terminal of the battery while the shorter lead is always connected to a negative terminal of the battery. In circuit (B) switch is present and is in its ON position. Only this makes the LED glow.

In a cell (such as a battery), the following energy conversion takes place: B: Chemical energy into electrical energy
Cells convert stored chemical energy into electrical energy through electrochemical reactions, providing power to operate devices and circuits.

The correct characteristic of an electrolyte is: D: It forms positive and negative ions.
Electrolytes are substances that, when dissolved in water or another solvent, dissociate into ions and thus become capable of conducting electricity.

The acid present in lemon juice that acts as an electrolyte is: D: Citric acid
Citric acid is a natural compound found in citrus fruits like lemons and limes, and it can conduct electricity when dissolved because it dissociates into ions.

In a dry cell, ammonium chloride serves as the electrolyte. This chemical is typically used in the form of a paste that facilitates the flow of ions within the cell, thus enabling the production of electrical energy through electrochemical reactions. The presence of ammonium chloride in the electrolyte helps to transfer ions between the anode and the cathode, which is crucial for the generation of electricity in these cells.

In a dry cell, the component that acts as the positive terminal is: D: A metal cap on the carbon rod
The metal cap attached to the carbon rod serves as the positive terminal, or cathode, in the construction of a dry cell. This setup is essential for completing the cell's circuit, allowing for the flow of electrons from the negative to the positive terminal.

A standard dry cell, commonly used in various household batteries like AA, AAA, C, and D sizes, typically produces a voltage of 1.5 volts. This voltage is a result of the chemical reactions occurring between the anode, cathode, and the electrolyte within the cell. The 1.5-volt output is sufficient for powering small devices and gadgets, making these cells ideal for everyday electronic applications.

When electric current is made to flow through a conductor, the correct answer is: A: Some amount of electrical energy is converted into heat energy.
This phenomenon, where electrical energy is converted into heat energy in a conductor, is described by Joule's law. As electrical current passes through a conductor, it encounters resistance, which results in the generation of heat. This is a common effect seen in many electrical appliances, such as heaters and incandescent light bulbs.

Nichrome is an alloy primarily composed of nickel and chromium, typically with about 80% nickel and 20% chromium by mass. This composition gives nichrome excellent resistance to high temperatures and oxidation, making it ideal for use in various heating elements. Its stability and resistance properties also ensure that it performs consistently over a wide range of temperatures and conditions, which is essential for applications requiring precise heating, such as in toasters, hair dryers, and industrial furnaces.

The splitting of a compound using electricity is called: A: Electrolysis
Electrolysis is the process where electrical energy is used to drive a chemical reaction which would not otherwise occur. This process is commonly used to decompose chemical compounds, often to extract a particular element from one of its naturally occurring and stable forms.

The principle involved in the glowing of an electric bulb is: B: Heating effect of current

In an electric bulb, particularly those with incandescent filaments, electrical current flows through the filament, usually made of tungsten. This current heats the filament to a high temperature, causing it to glow and emit light. This process is a direct application of the heating effect of electric current.

LEDs are extensively used to replace bulbs because they consume less electricity, have longer life and have more power.

Sea water is a superior conductor of electricity primarily because it contains a high concentration of dissolved salts, mainly sodium chloride. These salts dissociate into positive and negative ions, which enhance the water's ability to conduct electrical current. In contrast, distilled water lacks these ions, making it a poor conductor, while tap and rain water have lower concentrations of ions compared to sea water, resulting in lesser conductivity.

The effect of current responsible for the deflection of a compass needle in an electric field is: B: Magnetic effect of current

When electric current flows through a conductor, it generates a magnetic field around it. This magnetic field interacts with the magnetic field of a compass needle, causing it to deflect. This principle underlies the operation of devices such as electromagnets and electric motors.

The correct answer is: D: All of the above

The chemical effects of electric current are used in various industrial applications such as electroplating (coating objects with a thin layer of metal), galvanizing (applying a protective zinc coating to prevent rusting), and anodizing (an electrochemical process that thickens the oxide layer on metal surfaces, often for corrosion resistance). These processes rely on electric current to drive chemical reactions that alter the surface properties of materials.

The correct answer is: D: Distilled water

Distilled water is a poor conductor of electricity because it lacks dissolved ions, which are necessary to carry electric current. Unlike lemon juice, vinegar, and sea water—which contain ions and conduct electricity—distilled water is relatively pure and lacks these conductive particles.