A chemical cell or battery produces a constant flow of charge in one direction, which is defined as direct current (DC). Unlike alternating current (AC), which periodically reverses direction, DC maintains a steady polarity, making it ideal for portable electronic devices and chemical energy storage systems.

Electric current is defined as the rate of flow of electric charge through a conductor. Mathematically, it is expressed as I = Q/t, where I is the current in Amperes, Q is the charge in Coulombs, and t is the time in seconds. This fundamental relationship describes how much charge passes a specific point in a circuit per unit of time.

An ammeter is designed to measure the flow of electric current through a conductor. To ensure that the entire current passes through the device for accurate measurement, it must be connected in series with the load. Connecting it in parallel would create a short circuit or provide an incorrect reading due to current division.

Rutherford's model proposed that electrons revolve around the nucleus in circular orbits, similar to planets orbiting the sun. Because they are in constant motion, they are not stationary. This motion is essential to prevent the electrons from falling into the nucleus due to electrostatic attraction, although the model faced challenges regarding classical electromagnetic theory.

In 1897, J.J. Thomson conducted experiments with cathode ray tubes, demonstrating that cathode rays were composed of negatively charged particles, which he called 'corpuscles' and are now known as electrons. This discovery fundamentally changed the understanding of atomic structure, proving that atoms were not indivisible. His work earned him the Nobel Prize in Physics in 1906 for his investigation into the conduction of electricity by gases.

The Rutherford atomic model proposed that electrons orbit a dense, positively charged nucleus. However, according to classical electromagnetism, an accelerating charged particle like an electron should continuously emit radiation and lose energy, eventually spiraling into the nucleus. Rutherford's model could not explain why electrons remained in stable orbits, a problem later addressed by the Bohr model and quantum mechanics.

Rutherford's model proposed that electrons orbit the nucleus like planets. According to classical electrodynamics, an accelerating charge (the orbiting electron) must continuously radiate energy. This loss of energy would cause the electron to spiral into the nucleus, emitting a continuous range of frequencies during the process. This prediction contradicted the observed discrete line spectra of atoms, leading to the development of the Bohr model.

The electrostatic force between the nucleus and alpha particle follows Coulomb's inverse square law. Rutherford's scattering experiment confirmed the existence of a dense, positively charged nucleus. While both statements are scientifically accurate, the experiment itself is a historical event and not the physical derivation of the inverse square law.

Positive rays (or canal rays) consist of positively charged ions. Alpha particles are helium nuclei (He2+), which are also positively charged ions. Therefore, positive rays are often identified with alpha particles in the context of early atomic physics experiments.

Thomson's 'plum pudding' model proposed that electrons were embedded in a sphere of positive charge. While it accounted for electrical neutrality, it failed to explain the stability of the atom or the existence of discrete energy levels observed in atomic spectra, which were later addressed by the Bohr model.