Electric Changes and Fields - Lecture Notes

Vocabulary practice flashcards based on lecture notes covering the fundamental properties of electric charges, their motion states, units, and conservation laws.

Electrostatic

The balance of physics in which the charge is in rest.

Charge

An intensive property associated with matter due to which it freeduces and experiences electric field and magnetic field.

Charge "q" in Rest ($v=0$)

If charge is at rest it only freeduces electric field.

Charge "q" in Uniform Motion ($v = \text{const}$)

If charge is in uniform motion, it produce electric field and magnetic field.

Charge "q" in Non-uniform Motion ($v \neq \text{const}$)

If charge is in non-uniform motion, it produce electric field, magnetic field, and also radiate electromagnetic wave.

Positive Charge

A type of charge that occurs due to deficiency of electron.

Negative Charge

A type of charge that occurs due to excess of electron.

Coulomb ($c$)

The SI unit of charge.

State coulomb

The CGS unit of charge.

Faraday

The large practical unit of charge.

Franklin

The smallest unit of charge, also known as the CGS unit or State coulomb.

$1\,C$ conversion

$1\,C = 3 \times 10^9$ State Coulomb.

Dimension Formula of Charge

$q = [M^0 L^0 T^1 A^1]$ (Current $\times$ time).

Additive property

Charge is a scalar quantity that follows the scalar addition rule where total charge $Q_{net} = q_1 + q_2 + ... + q_n$ or $Q = \sum q_i$.

Conservation of Charge

Charge can neither be created nor be destroyed and can only transfer from one body to another.

Glass rod and silk cloth example

When a glass rod is rubbed with silk cloth, negative charge is transferred from glass rod to the silk. Silk cloth becomes negative while glass rod becomes positive, in accordance with the law of conservation of charge.

Nuclear fission (charge conservation example)

In the reaction $n^0 + U_{92}^{235} \rightarrow Ba_{56}^{144} + Kr_{36}^{89} + 3n^0$, the initial charge ($0 + 92 = 92$) is equal to the final charge ($56 + 36 + 0 = 92$).

Charge and mass relationship

A charge cannot exist without mass, though mass can exist without charge. For example, photons have zero rest mass and no charge.

Mass of a body given a positive charge

The mass of the body decreases.

Mass of a body given a negative charge

The mass of the body increases.

Relativistic mass formula

$m = \frac{m_0}{\sqrt{1 - \frac{v^2}{c^2}}}$ indicating mass increases as speed increases.

Rest mass ($m_0$)

The mass of the particle when it is at rest (not moving).

Charge independence

Charge is independent of the frame of reference; the charge on a body does not change regardless of its speed.