Electricity and Magnetism

Good absorbents of electromagnetic radiation are also good radiators because materials that absorb energy well tend to emit energy efficiently as well, according to Kirchhoff's law of thermal radiation.

Charles-Augustin de Coulomb discovered the law of attraction and repulsion between electric charges, formulating Coulomb's law which quantifies the force between charged objects.

As temperature increases, the conductivity of metals decreases because the increased thermal vibrations of the metal ions scatter the conduction electrons more, reducing their mobility.

One mega ohm (MΩ) is equal to 10^6 ohms, which means one million ohms. This is a standard unit conversion in electrical resistance. Among the options given, option A (10^6 ohm) correctly represents one mega ohm. The original correct answer was C (10^7 ohm), which is incorrect. Therefore, the correct answer is option A.

Electrons are the charge carriers in metals because they are loosely bound to atoms and can move freely, unlike protons which are tightly bound in the nucleus. Their small size and negative charge are true but not the primary reason for their mobility in metals.

The magnetic field inside the core of a toroid depends on both the current flowing through the coil and the number of turns per unit length. According to Ampère's law, the magnetic field at a radius r inside the toroid is given by B = (μ * N * I) / (2πr), where N is the total number of turns, I is the current, and μ is the permeability of the core material. Thus, the magnetic field depends on the current and the number of turns, not just one or the other. The field is not zero inside the toroid; it is confined within the core region and varies with radius.

Conductivity is the measure of a material's ability to conduct electric current, and its unit is the mho, which is the reciprocal of the ohm (unit of resistance).

Gamma rays are electromagnetic radiation and have no charge, so they are not deflected by electric or magnetic fields, unlike alpha and beta rays which are charged particles and do get deflected.

The SI unit of dipole moment is coulomb-meter (Cm), which represents the product of charge and distance. Debye is a commonly used unit in chemistry but is not an SI unit. Weber is the SI unit of magnetic flux, and Coulomb is the unit of electric charge.

A bird on a high tension wire does not get electrocuted because it does not complete a circuit; there is no closed path for current to flow through its body to the ground.

The SI unit of electric current is the ampere, which measures the flow of electric charge per second. Coulomb is the unit of electric charge, volt is the unit of electric potential, and watt is the unit of power.

A rectifier is an electrical device that converts alternating current (AC) to direct current (DC). The other options do not perform this function: an anemometer measures wind speed, a battery stores electrical energy, and a galvanometer measures electric current.

Ultraviolet (UV) light has enough energy to ionize atoms and molecules, placing it in the category of ionizing radiation rather than non-ionizing. Visible light does not have sufficient energy to ionize, and 'None' is incorrect.

The coulomb (C) is the SI unit of electric charge, not velocity, temperature, or mass. Therefore, none of the given options A, B, or C are correct, making option D the correct choice.

Vacuum tubes were widely used in early electronics for amplification and switching but have been replaced by transistors, which are smaller, more reliable, and energy-efficient semiconductor devices.

The SI unit of electric charge is the Coulomb, which quantifies the amount of electric charge transported by a current of one ampere in one second.

MSI stands for 'Medium Scale Integrated Circuits,' which refers to integrated circuits containing hundreds of logic gates. This is a standard term in digital electronics.

IC stands for 'Integrated Circuit,' which is a set of electronic circuits on a small chip of semiconductor material. This is the most common and widely accepted meaning in electronics.

DC stands for 'direct current,' which is a type of electrical current that flows in one direction only.

LED stands for Light Emitting Diode, which is a semiconductor device that emits light when an electric current passes through it. The other options do not accurately represent the acronym LED.

Space waves are electromagnetic waves that travel directly from the transmitting antenna to the receiving antenna and are used for line of sight (LOS) communication, such as in TV and FM radio transmission.