Compilation of Electrical Engineering Objective Type Questions

A comprehensive collection of vocabulary terms and definitions covering basic electrical engineering, magnetism, circuitry, machines, and illumination based on the lecture questions.

Resistance of a Conductor

The hindrance by which the conductor opposes the flow of the current.

Specific Resistance ($\rho$)

The resistance of a conductor which has a length of $1\,m$ and cross-section of $1\,m^2$ at $20^{\circ}C$. It depends only on the nature of the material of the conductor.

Joule's Law

States that the heat produced in a current carrying conductor is proportional to the square of the current ($I^2$).

Joule's Mechanical Equivalent of Heat ($J$)

A value equal to $4.2\,\text{Joules per calorie}$.

Temperature Coefficient

The increase in resistance per ohm per degree centigrade.

Ohm's Law Curve

A linear curve, provided that the temperature remains constant.

Three Effects of Current

The presence of current is made known by heating, magnetic, and chemical effects.

Parallel Circuit Conductance

For three elements connected in parallel, the combined conductance is $G_1 + G_2 + G_3$.

International Ohm

Defined in terms of the resistance of a column of mercury.

Thermistor

A component that has a negative coefficient of resistance.

Lodestone

A name for a natural magnet.

Residual Magnetism

The magnetism that remains in a magnet after the magnetizing force has been removed.

Permeance

The magnetic circuit analog to conductance in an electrical circuit.

Permeability

The conductivity of a material for magnetic lines of force.

Magnetic Flux Density ($B$)

The ratio of magnetic flux ($\phi$) to the area ($A$) under its influence, given by $B = \frac{\phi}{A}$.

Permeability of Free Space

A value defined as $4\pi \times 10^{-7}\,Hm^{-1}$.

Curie Temperature

The characteristic temperature above which a ferromagnetic material's properties change significantly.

Eddy Current Loss Mitigation

Minimized by increasing the resistance of the magnetic medium or using laminated cores.

Lenz's Law

States that the induced emf and current always oppose the cause producing them.

Inductive Time Constant

The ratio $L/R$, representing the time it takes for the current in an inductive circuit to rise to $63\%$ of its final steady state value.

Degaussing

The process of demagnetizing metallic parts.

Absolute Permittivity of Vacuum

Taken as $8.854 \times 10^{-12}\,\text{farad/meter}$.

One Farad

Defined as one coulomb per volt.

Electrochemical Equivalent

The mass of an element liberated per unit quantity of electricity passed through an electrolyte.

Local Action

An internal short circuit condition in a battery caused by impurities in an electrolyte; it can be rectified by amalgamating the zinc electrode with mercury.

Secondary Cell advantage

Unlike a primary cell, it can be recharged.

Ampere Hour Capacity

The capacity of a battery which depends primarily on the area of the plates.

DC Generator Output

The output of a single loop generator is pulsating d.c.; a smooth output is obtained through the design of the commutator.

Commutator Function (Motor)

In a dc motor, it converts dc to ac to provide the correct current flow in the armature conductors.

DC Shunt Motor Speed

Directly proportional to back emf ($E_b$) and inversely proportional to flux ($\phi$).

Root Mean Square (rms) Value

The effective value of a sine wave, equal to $0.707 \times \text{max. value}$.

Form Factor

The ratio of the rms value to the average value; for a pure sine wave, it is $1.11$.

Resonant Frequency ($f$)

The frequency at which $X_L = X_C$, calculated as $f = \frac{1}{2\pi \sqrt{LC}}$. At this frequency, power factor is unity.

Thevenin's Theorem

Reduces a network to an equivalent circuit consisting of a single voltage source and a series impedance.

Transformer Rating

Transformers are rated in $kVA$ ($\text{kilo-volt-amperes}$).

Transformer Breather

A component used to extract moisture from the air used for cooling/expansion in the conservator.

Skin Effect

The phenomenon where a conductor carries more current on its surface than in its core.

Corona Effect

An electrical discharge that causes increased energy loss and produces ozone, which can corrode materials.

Luminous Intensity

Luminous flux per unit solid angle, expressed in candela.

Lux

The unit of illumination, defined as the luminous flux per unit area of the surface.