EU1

Question 1

These are materials whose electrons are held
firmly to their nucleus.

Answer 1

INSULATORS

Question 2

It is an instrument used to measure current
and must be connected in series with the
circuit.

Answer 2

AMMETER

Question 3

It is an instrument used to measure p.d. and
must be connected in parallel with the part of
the circuit whose p.d. is required.

Answer 3

VOLTMETER

Question 4

These are materials that contain electrons that
are loosely connected to the nucleus and can
easily move through the material from one
atom to another.

Answer 4

CONDUCTORS

Question 5

It is an instrument for measuring resistance.

Answer 5

OHMMETER

Question 6

It used to measure voltage, current and
resistance. An ‘Avometer’ is a typical example.

Answer 6

MULTIMETER/ UNIVERSAL INSTRUMENT

Question 7

It is used to observe waveforms and to
measure voltages and currents It involves a
spot of light moving across a screen.

Answer 7

CATHODE RAY OSCILLOSCOPE (CRO)

Question 8

A complete conducting path is necessary to
and from the source of electrical energy.

Answer 8

POTENTIAL (p.d) or VOLTAGE

Question 9

The flow of electric current is subject to friction.
This friction, or opposition.

Answer 9

RESISTANCE (R)

Question 10

The system of units used in engineering and
science is the Systeme Inter- nationale
d’Unites (International system of units. It is
based on the metric system. This was
introduced in 1960 and is now adopted by the
majority of countries as the official system of
measurement.

Answer 10

SI UNITS

Question 11

It uses combinations of basic units

Answer 11

DERIVED SI UNITS

Question 12

The unit is the coulomb (C) where
one coulomb is one ampere second. (1
coulomb D 6.24 ð 1018 electrons).

Answer 12

CHARGE

Question 13

The unit is the newton (N) where one
newton is one kilogram metre per second
squared.

Answer 13

FORCE

Question 14

The unit is the joule (J) where one joule is one newton metre.

Answer 14

WORK

Question 15

The unit is the watt (W) where one
watt is one joule per second. Power is defined
as the rate of doing work or transferring
energy.

Answer 15

POWER

Question 16

The unit of electric potential is the volt (V)
where one volt is one joule per coulomb. One
volt is defined as the difference in potential
between two points in a conductor which, when
carrying a current of one ampere, dissipates a
power of one watt, i.e.

Answer 16

ELECTRICAL POTENTIAL AND EMF

Question 17

The unit of electric resistance is the ohm (Z)
where one ohm is one volt per ampere. It is
defined as the resistance between two points
in a conductor when a constant electric
potential of one volt applied at the two points
produces a current flow of one ampere in the
conductor.

Answer 17

RESISTANCE AND CONDUCTANCE

Question 18

The property of this ‘‘pair of plates’’ which
determines how much charge corresponds to a
given p.d. between the plates

Answer 18

Capacitance

Question 19

Devices specially ‘‘constructed to possess
capacitance’’. Has the ability to store a quantity of static electricity

Answer 19

Capacitors

Question 20

usually ‘‘consist of two sets of metal plates’’
(such as aluminum) one fixed, the other
variable.

Answer 20

Variable air capacitors

Question 21

It is ‘‘easily obtained in thin sheets’’ and is a
good insulator. coated on both sides with a thin layer of silver which forms the plates.

Answer 21

Mica Capacitors

Question 22

A typical capacitor where ‘‘the length of
the roll corresponds to the capacitance
required’’. The whole is usually impregnated with oil or wax to exclude moisture, and then placed in a plastic or aluminum container for protection.

Answer 22

Paper Capacitor

Question 23

These are “made in various forms”, each type
of construction depending on the value of the
capacitance required.

Answer 23

Ceramic Capacitors

Question 24

Some ‘‘plastic materials’’ such as ‘‘polystyrene
and Teflon can be used as dielectrics’’.

Answer 24

Plastic Capacitors

Question 25

''Have a very high capacitance'' with a small physical size when used at a low temperature.

Answer 25

Titanium Oxide Capacitors

Question 26

''Construction is similar to the paper capacitor'' with aluminum foil used for the plates and with a thick absorbent material, such as paper, impregnated with an electrolyte (ammonium borate), separating the plates.

Answer 26

Electrolytic Capacitors

Question 27

When a capacitor has been ''disconnected'' from the supply it may still be charged and it may still retain this charge for some considerable time.

Answer 27

Discharging Capacitors

Question 28

the ''name given to the property of a circuit'' whereby there is an e.m.f induced into the circuit by the change of flux linkages produced by a current change.

Answer 28

Inductance

Question 29

When the e.m.f is ''induced in the same circuit'' as that in which the current is changing

Answer 29

Self Inductance (L)

Question 30

When the e.m.f is ''induced in a circuit by a change of flux'' due to current changing in adjacent circuit

Answer 30

Mutual Inductance (M)

Question 31

Unit of Inductance

Answer 31

Henry (H)

Question 32

'The direction of an induced e.m.f. is always such that it ''tends to set up a current opposing the motion or the change of flux'' responsible for inducing that e.m.f.'.

Answer 32

Lenz’s Law states

Question 33

states that if we arrange our thumb, forefinger and middle finger of the right-hand perpendicular to each other, then the thumb points towards the direction of the motion of the conductor relative to the magnetic field, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the induced current.

Answer 33

Fleming's Right Hand Rule

Question 34

''used when the property of inductance is required in a circuit''. possesses an ability to store energy.

Answer 34

Inductors

Question 35

If a ''current changing from 0 to I amperes'', produces a flux change from 0 to Φ Webers, then dI = I and do = Ф.

Answer 35

Inductance of a coil

Question 36

''produced by generators at power stations'' and then distributed by a vast network of transmission lines to industry and for domestic use. It is easier and cheaper to generate alternating current than direct current.

Answer 36

ELECTRICITY

Question 37

vast network of transmission lines

Answer 37

NATIONAL GRID SYSTEM

Question 38

If values of quantities which vary with ''time t are plotted to a base of time'', the resulting graph is called waveform.

Answer 38

WAVEFORM

Question 39

One complete series of values

Answer 39

CYCLE

Question 40

The time taken for an alternating quantity to complete one cycle.

Answer 40

PERIOD/ PERIODIC TIME (T)

Question 41

''The number of cycles completed in one second'', the supply and is measured in hertz, Hz. The standard frequency of the electricity supply in Great Britain is 50 Hz.

Answer 41

FREQUENCY (F)

Question 42

are ''the values of the alternating quantities'' at any instant of time. They are represented by small letters, i, v, e etc

Answer 42

INSTANTANEOUS VALUE

Question 43

The largest value reached in a half cycle

Answer 43

-PEAK VALUE -MAXIMUM VALUE -CREST VALUE -AMPLITUDE OF WAVEFORM

Question 44

the average value measured over a half cycle, (since over a complete cycle the average value is zero).

Answer 44

AVERAGE OR MEAN VALUE

Question 45

The ''area under the curve'' is found by approximate methods

Answer 45

-TRAPEZOIDAL RULE -MID-ORDINATE RULE -SIMPSON’S RULE

Question 46

an alternating current is that ''current which will produce the same heating effect'' as an equivalent direct current.

Answer 46

EFFECTIVE VALUE

Question 47

The effective value

Answer 47

ROOT MEAN SQUARE (RMS) VALUE

Question 48

A rotating vector

Answer 48

PHASOR

Question 49

The current IR and applied voltage VR are in phase

Answer 49

PURELY RESISTIVE AC CIRCUIT

Question 50

''in purely inductive ac circuit'', opposition to the flow of alternating current

Answer 50

INDUCTIVE REACTANCE, XL

Question 51

the current Ic leads the applied voltage Vc by 90 degrees

Answer 51

PURELY CAPACITIVE AC CIRCUIT

Question 52

''in purely capacitive ac circuit'', opposition to the flow of alternating current

Answer 52

CAPACITIVE REACTANCE, Xc

Question 53

In an a.c. circuit containing inductance L and resistance R, the applied voltage V is the phasor sum of VR and VL, and thus the current I lags the applied voltage V by an angle lying between 0° and 90° (depending on the values of VR and VL), shown as angle Φ . In any series circuit the current is common to each component and is thus taken as the reference phasor.

Answer 53

R–L SERIES A.C. CIRCUIT

Question 54

In an a.c. series circuit containing capacitance C and resistance R, the applied voltage V is the phasor sum of VR and VC (see Figure 15.10) and thus the current I leads the applied voltage V by an angle lying between 0° and 90° (depending on the values of VR and VC), shown as angle Φ.

Answer 54

R–C SERIES A.C. CIRCUIT

Question 55

In an a.c. series circuit containing resistance R, inductance L and capacitance C, the applied voltage V is the phasor sum of VR, VL and VC. VL and VC are anti-phase, i.e. displaced by 180°, and there are three phasor diagrams possible — each depending on the relative values of VL and VC

Answer 55

R–L-C SERIES A.C. CIRCUIT

Question 56

- in an ac circuit, it is the ratio: applied voltage v / current I

Answer 56

IMPEDANCE, Z

Question 57

effect in an R-L-C ac circuit, when XL = XC, the applied voltage V and the current I are in phase

Answer 57

SERIES RESONANCE

Question 58

''often described as an acceptor circuit'' since it has its minimum impedance, and thus maximum current, at the resonant frequency

Answer 58

SERIES RESONANCE CIRCUIT

Question 59

''the value of power at any instant'' is given by the product of the voltage and current at that instant, i.e. the instantaneous power, p = vi, as shown by the broken lines.

Answer 59

POWER IN AC CIRCUITS

Question 60

If each of the voltage phasors is multiplied by I is obtained.

Answer 60

POWER TRIANGLE

Question 61

BASIC ELECTRICAL MEASURING INSTRUMENTS

Answer 61

AMMETER VOLTMETER OHMMETER MULTIMETER/ UNIVERSAL INSTRUMENT

Question 62

Practical Types of Capacitor

Answer 62

1. Variable air capacitors (VAC) 2. Mica Capacitors (MC) 3. Paper Capacitor (PC) 4. Ceramic Capacitors (CC) 5. Plastic Capacitors (PC) 6. Titanium Oxide Capacitors (TOC) 7. Electrolytic Capacitors (EC)

Question 63

''defined as the quantity of electricity'' which flows past a given point in an electric circuit when a current of one ampere is maintained for one second.

Answer 63

coulomb

Question 64

''defined as the force'' which, when applied to a mass of one kilogram, gives it an acceleration of one metre per second squared.

Answer 64

Newton

Question 65

''defined as the work done or energy transferred'' when a force of one newton is exerted through a distance of one metre in the direction of the force.

Answer 65

joule