Correct Answer: A. 300 Million m/s

The correct answer is A. 300 Million m/s. The speed of light in a vacuum is approximately 299,792,458 meters per second, often rounded to 300 million meters per second for simplicity. This value is a fundamental constant in physics and is denoted by the symbol “c”

Correct Answer: A. 343 m/s

The speed of sound in dry air at 20°C is approximately 343 meters per second (m/s). This value is affected by factors such as temperature, pressure, and humidity. In dry air at standard conditions, sound travels at this speed, which is commonly used as a reference value in physics and engineering calculations involving sound propagation

Correct Answer: C. Echo

The correct answer is C. Echo. When sound waves reflect off surfaces such as floors, ceilings, or walls and return to the listener’s ears after a brief delay, it creates an audible repetition of the original sound, known as an echo. Echoes occur due to the reflection of sound waves off solid surfaces, and they can alter the perception and quality of the original sound.

Correct Answer: D. Due to attraction of North Pole and Repulsion of Western Pole

The correct answer is D. Due to the attraction of the North Pole and repulsion of the South Pole. This phenomenon is due to the Earth’s magnetic field, which has a north magnetic pole and a south magnetic pole. A magnet, if allowed to move freely, aligns itself with this magnetic field, with its north pole pointing towards the Earth’s geographic north pole and its south pole pointing towards the Earth’s geographic south pole. This behavior is because opposite magnetic poles attract each other, while like poles repel each other

Correct Answer: D. All of these

An electric current can indeed produce various effects. Let’s break down the options:

A. Chemical Effect: Electric current can cause chemical changes in certain materials, such as electrolysis, where a chemical reaction occurs due to the flow of electric current.

B. Magnetic Effect: When electric current flows through a conductor, it generates a magnetic field around it, known as the magnetic effect of electric current.

C. Heating Effect: When electric current passes through a conductor with resistance, such as a filament in a light bulb or a heating element in an electric stove, it generates heat due to the resistance of the material.

Therefore, the correct answer is:

D. All of these: All of the listed options are effects produced by electric currents.

Correct Answer: B. Kilowatt hour

The unit of home electricity energy consumption is typically measured in kilowatt-hours (kWh). So, option B, “Kilowatt hour,” is the correct answer. A kilowatt-hour (kWh) is a unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour. It is commonly used as a billing unit for energy consumed by residential and commercial customers. For example, if a device with a power rating of 1 kilowatt (or 1000 watts) operates continuously for one hour, it would consume 1 kilowatt-hour of energy. In practical terms, it’s a measure of how much energy is used over time, and it’s what you’re typically billed for by your utility company