Learn Science with Free Lessons & Tips

• The direction of conventional current is considered to be the direction of flow of positive charge, which is opposite to the direction of the flow of electrons. So, conventional current flows from the positive terminal of a battery or voltage source towards the negative terminal.

• The frequency of an alternating current (AC) is the number of complete cycles per second and is measured in hertz (Hz). In India, the standard frequency of AC power supply is 50 Hz. Alternating current is considered advantageous over direct current (DC) for long-range transmission of electric energy because it can be easily stepped up or down in voltage using transformers, which allows for efficient transmission over long distances with minimal energy loss.

• An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. To transform a soft iron piece into an electromagnet, a coil of wire is wound around the iron core, and when electric current passes through the coil, it magnetizes the iron core, creating a temporary magnet.

• One advantage of ozone is its role in the stratosphere, where it forms the ozone layer that absorbs harmful ultraviolet (UV) radiation from the sun, protecting life on Earth from excessive UV exposure. One disadvantage of ozone is its harmful effects on human health and the environment when present in high concentrations in the lower atmosphere, contributing to smog formation and respiratory problems.

Recycling is generally considered better than reuse because it involves processing materials to create new products, reducing the need for virgin resources and minimizing waste. For example, recycling paper saves trees and energy compared to reusing paper, which may not be feasible due to degradation or contamination.

Three measures to lower the use of coal and petroleum include:

1. Increasing energy efficiency and conservation measures to reduce overall energy consumption.
2. Promoting the use of renewable energy sources such as solar, wind, and hydropower to replace coal and petroleum-based energy sources.
3. Implementing policies and incentives to encourage the adoption of alternative transportation fuels, such as electric vehicles and biofuels, to reduce reliance on petroleum.