CBSE Class 8 Science Exemplar Chapter 14: Chemical Effects of Electric Current NCERT Solutions

Solution: The correct answer is (d) chemical, heating, and magnetic effects. Electric current exhibits multiple effects when passed through different materials or circuits.

Explanation:

1. Chemical Effect: When an electric current is passed through a conducting liquid (electrolyte), it can cause chemical reactions. For example, electrolysis of water produces hydrogen and oxygen gas. This is a chemical effect.

2. Heating Effect: When current flows through a conductor with resistance, electrical energy is converted into heat energy, causing the conductor to heat up. This is observed in devices like electric heaters and the filament of a light bulb.

3. Magnetic Effect: An electric current flowing through a wire creates a magnetic field around it. This principle is used in electromagnets and electric motors.

Therefore, electric current can produce all three effects: chemical, heating, and magnetic.

Solution: The conclusion is (a) higher current is flowing through the circuit in setup A.

Explanation:

The brightness of the bulb is directly related to the amount of electric current flowing through it. A brighter glow indicates a larger current. Since the bulb in setup A glows more brightly than the bulb in setup B, it means that a higher electric current is flowing through the circuit in setup A.

This difference in current suggests that solution A is a better conductor of electricity than solution B. Solutions that are good conductors allow more charge to flow through them per unit time, resulting in a higher current.

Solution: The waste of the factory should be disposed of (d) according to the disposal guidelines of the local authority.

Explanation:

Electroplating factories often use chemicals that can be harmful to the environment. The waste produced can contain toxic metals and other substances that can pollute water bodies like rivers and ponds, and harm soil and crops if disposed of improperly. Therefore, it is crucial to follow the specific regulations and guidelines set by the local authorities for the safe and environmentally responsible disposal of industrial waste from electroplating units.

Solution: This indicates (a) the chemical effect of current.

Explanation:

The passage of electric current through a conducting solution can cause chemical reactions. One of the observable outcomes of these chemical reactions is a change in the color of the solution. This phenomenon is a direct manifestation of the chemical effect of electric current.

The heating effect is related to the rise in temperature, and the magnetic effect is related to the production of a magnetic field. Neither of these typically causes a change in the color of the solution itself.

Solution: The question asks to identify a solution that will not conduct electricity. Generally, pure water does not conduct electricity well because it contains very few free ions. However, many common liquids like distilled water, sugar solution, or alcohol are poor conductors. To provide a specific answer, more options would be needed. Typically, solutions that do not contain free-moving ions, such as pure water, distilled water, or solutions of non-electrolytes like sugar or alcohol, will not conduct electricity effectively.