Main Definitions

Question 1

Alternating current (a.c)

Answer 1

Current which varies in direction an magnitude.

Question 2

Ampere (A)

Answer 2

The unit of electric CURRENT (Symbol: I)

Question 3

Candela (cd)

Answer 3

The unit of luminous intensity (Symbol : I )

Question 4

Coulomb (c)

Answer 4

The unit of electric quality (symbol : Q )

Question 5

Cycle

Answer 5

One complete set of changes on an a.c waveform.

Question 6

Eddy current

Answer 6

The current persuade into a magnetic core by mutual inductance.

Question 7

Electromotive force (e.m.f)

Answer 7

The voltage measured across a source of supply when no current is flowing (open-circuit voltage).

Question 8

Frequency(f)

Answer 8

The number of cycles completed in a second, for example, 50 cycles per seconds Unit: Hertz (Hz)

Question 9

Henry(H)

Answer 9

The unit of self,or mutual, inductance

Question 10

Hysteresis

Answer 10

The lag which takes place in a magnetic circuit between a changing magnetizing force (H) and the flux density (B) which it produces.This lag between the magnetizing force and resultant flux density causes an energy loss termed a hystersis loss

Question 11

Impedance (Z)

Answer 11

The total opposition to a flow of alternating current in a circuit (unit: ohm)

Question 12

Joule (J)

Answer 12

A unit of electrical energy

Question 13

Kilowatt-hour(kWh)

Answer 13

The practical unit of electrical energy

Question 14

Lumen

Answer 14

This is the unit if luminous flux which is the measure of light emitted from a source (Symbol: F)

Question 15

Ohm’s Law

Answer 15

States that the current (I) flowing in a circuit is correlative to the voltage (V) and inversely proportional to the resistance (R), at a constant temperature

Question 16

Ohm(Ω)

Answer 16

The unit of resistance

Question 17

Potential difference (p.d)

Answer 17

The voltage measured across a circuit , or part of a circuit, when a current is flowing
(the closed-circuit voltage)

Question 18

Power factor (p.f)

Answer 18

Is expressed as the cosineof the angle () of the phase difference between voltage and current in an a.c circuit. It may also be stated as the ratio between true power (kW) and apparent power (kVA)

Question 19

Resistivity

Answer 19

The resistance of a unit cube of a material, measured across opposite faces of the cube.
Symbol ρ (rho)

Question 20

Root mean square (r.m.s) value

Answer 20

That value of alternating voltage,or current, which gives the same heating, or lighting, effect as a similar value of direct voltage , current . Supply voltages (a.c) are always given in r.m.s values

Question 21

Temperature coefficient

Answer 21

The temperature coefficient of a material is the increase in the resistance of a one ohm resistor of that material when it is subjected to a rise in temperature of 1 degC°. Symbol α (Alpha)

Question 22

Volt(V)

Answer 22

The unit of electric pressure

Question 23

Watt(W)

Answer 23

The unit of electric power (1000W=1kW)

Question 24

What is a conductor?

Answer 24

A conductor is a material which offers a low resistance to a flow of current

Question 25

An insulator is?

Answer 25

An insulator is a material which offers a very high resistance to a flow of current.

Question 26

A cable is?

Answer 26

A length of insulated single conductor (solid or stranded(, or two or more such conductors, each provided with its own insulation, which are laid up together.

Question 27

What is resistance?

Answer 27

A resistance is a friction that a material presents to a flow of current.

Question 28

What is temperature coefficient?

Answer 28

It is the relative change in resistance per degree change in temperature

Question 29

PVC

Answer 29

Polyvinyl chloride

Question 30

EMT

Answer 30

Electrical metallic tubing

Question 31

Circuit breaker

Answer 31

A mechanical switching devices capable of making, carrying and breaking currents..