Tamil Nadu HSE First Year Basic Electrical Engineering flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Coulomb

The SI unit of electric charge, equal to the charge of about 6.24 × 10^18 electrons; one ampere carries one coulomb per second.

Ampere

The SI unit of electric current, defined as the flow of one coulomb of charge per second past a point in a circuit.

Kilowatt-hour

A unit of electrical energy equal to 1000 watts used for one hour; it equals 3.6 million joules and is the domestic billing unit.

Ohm's law

For a metallic conductor at constant temperature, current is directly proportional to applied voltage, giving V = IR.

Non-ohmic conductor

A device whose resistance changes with voltage or current, so its V–I graph is not a straight line through the origin, such as a diode.

Voltage divider rule

In a series circuit, the voltage across one resistor equals total voltage multiplied by that resistance divided by total series resistance.

Current divider rule

In parallel branches, the current in one branch equals total current multiplied by the other branch resistance divided by the sum of both resistances.

Resistivity

A material property, symbol rho, giving resistance of a unit cube; resistance equals resistivity times length divided by cross-sectional area.

Electrical power

The rate of energy transfer in a circuit, measured in watts, calculated as P = VI or P = I squared R or P = V squared divided by R.

Joule's law of heating

The heat produced in a resistor equals I squared times resistance times time in seconds, expressed in joules.

Efficiency

The ratio of useful output power to total input power, usually expressed as a percentage and always less than 100 percent.

Magnetic flux density

Flux per unit area perpendicular to the field, symbol B, measured in tesla or webers per square metre.

Fleming's left-hand rule

A rule giving the direction of force on a current-carrying conductor in a magnetic field: thumb force, first finger field, second finger current.

Magnetic reluctance

The opposition of a magnetic circuit to flux, equal to length divided by permeability times area, analogous to resistance.

Faraday's law

The emf induced in a coil equals the negative rate of change of magnetic flux linkage, so faster flux change gives larger emf.

Lenz's law

The direction of an induced emf is such that it opposes the change in flux that produced it, explaining the negative sign in Faraday's law.

Self-inductance

The property of a coil by which a changing current in it induces a back emf in itself, measured in henries.

Eddy currents

Circulating currents induced in a solid conducting core by changing flux, causing heating; reduced by using laminated cores.

Back emf

The emf induced in a motor armature that opposes the supply voltage, equal to V minus armature current times armature resistance.

Lap winding

An armature winding in which the number of parallel paths equals the number of poles, suited to high-current low-voltage machines.

Motor starter

A device that limits the large starting current drawn by a DC motor, since back emf is zero at standstill.

RMS value

The effective value of an alternating quantity, equal to peak value divided by root two, or 0.707 times peak for a sine wave.

Power factor

The cosine of the phase angle between voltage and current in an AC circuit, equal to resistance divided by impedance.

Inductive reactance

The opposition offered by an inductor to alternating current, equal to two pi times frequency times inductance, in ohms.

Series resonance

The condition in a series RLC circuit where inductive and capacitive reactances are equal, giving minimum impedance and maximum current.

Earth wire

A protective conductor connecting metal parts of an appliance to earth, carrying fault current away and preventing electric shock.

Miniature circuit breaker

An automatic switch that trips on overload or short circuit and can be reset manually, replacing a fuse in modern installations.

Two-way switch

A switch with one common terminal and two ways, used in pairs so a lamp can be controlled from two different positions.

Megger

An instrument that measures insulation resistance in megohms by applying a high test voltage to a de-energized circuit.

Ammeter connection

An ammeter is connected in series with the circuit and has very low resistance so it does not reduce the current being measured.

Energy meter

An instrument that integrates power over time and records electrical energy consumed in kilowatt-hours for billing purposes.

Meter bridge

A laboratory instrument based on the Wheatstone bridge used to measure unknown resistance accurately by balancing two resistance ratios.