Electronics III

Question 1

Electric current is the flow of ________ _______.

Answer 1

electric charge

Question 2

Electric charge is carried by particles such as _________ and _____.

Answer 2

electrons

ions

Question 3

In metals, the charge carriers are negatively charged __________ ________.

Answer 3

conduction electrons

Question 4

Conduction electrons move about inside the ______, repeatedly _________ with each other and the fixed positive _____ of the metal.

Answer 4

metal
colliding
ions

Question 5

Good conductors have many free to move ________ ________.

Answer 5

charge carriers

Question 6

Insulators have few ________ ________.

Answer 6

charge carriers

Question 7

When the ___________ of a semiconductor is _________ more charge carriers are produced and the semiconductor turns from an _________ into a _________.

Answer 7

temperature
increased
insulator
conductor

Question 8

In electric circuits the current is considered to flow out of the ________ terminal of a power supply and into the _________ terminal.

Answer 8

positive

negative

Question 9

A _______ gives each electron a fixed amount of _______.

Answer 9

battery

energy

Question 10

Chemical energy is transformed into ________ potential energy.

Answer 10

electrical

Question 11

______ has to be done to pass electrons through devices like the bulb.

Answer 11

Work

Question 12

Metals and other good conductors have very ____ resistivities.
(e.g. copper = 1.7 x 10 – 8 Ωm)

Answer 12

low

Question 13

Good insulators have very _____ resistivities.

e.g. PVC = 1.0 x 10 + 14 Ωm

Answer 13

high

Question 14

Semiconductors have ___________ resistivities.

e.g. silicon = 2.3 x 10 + 3 Ωm

Answer 14

intermediate

Question 15

Filament lamp, resistance __________ at higher currents due to increasing ___________.

Answer 15

increases

temperature

Question 16

A filament lamp does not obey ______ law.

Answer 16

Ohm’s

Question 17

Thermistor, resistance __________ with increasing temperature.

Answer 17

decreases

Question 18

A thermistor obeys Ohm’s law if the ___________ remains _________.

Answer 18

temperature

constant

Question 19

Metallic conductors, resistance _________ relatively _______ with temperature.

Answer 19

increases

slowly

Question 20

Positive ions within a conductor _______ more with increasing temperature

Answer 20

vibrate

Question 21

Semiconductors, resistance __________ relatively ________ with temperature.

Answer 21

decreases

quickly

Question 22

At any junction in a circuit, the total current ________ the junction is equal to the total current _________ the junction.

Answer 22

leaving

entering

Question 23

Resistors in series pass the same ________.

Answer 23

current

Question 24

The total _______ across two resistors, V, is equal to the sum of the individual voltage V1 and V2.
V = V1 + V2

Answer 24

voltage

Question 25

The total resistance is always ________ than any of the individual resistances.

Answer 25

greater

Question 26

Resistors in parallel all have the same _______.

Answer 26

voltage

Question 27

The total _______ through the two resistors, I, is equal to the sum of the individual currents I1 and 12.
I = I1 + I2

Answer 27

current

Question 28

The total resistance is always ________ than any of the individual resistances.

Answer 28

smaller

Question 29

When an electric ________ flows through an electrical conductor the ___________ of the conductor causes the conductor to be _______.

Answer 29

current
resistance
heated

Question 30

A car battery has an emf of about _____.

Answer 30

12V

Question 31

A high voltage power supply sometimes has a large protective ________ resistance.

Answer 31

internal

Question 32

Internal resistance limits the _______ that can be supplied to be well below the fatal level of about _____.

Answer 32

current

50 mA

Question 33

A potential divider consists of ____ or more resistors connected in ______ across a source of ______ potential difference.

Answer 33

two
series
fixed

Question 34

A potential divider is used in many circuits to control the level of an _______.

Answer 34

output

Question 35

List two examples of using a potential divider

Answer 35

1. Volume control

2. Automatic light control

Question 36

A capacitor is a device for storing _________ charge.

Answer 36

electrical

Question 37

Most capacitors consist of two parallel __________ (plates) separated by a ________.

Answer 37

conductors

dielectric

Question 38

A dielectric is a material which is a _____ conductor of electricity however it can be _________ by an applied _______ field.

Answer 38

poor
polarised
electric

Question 39

Uses of capacitors include:

Answer 39

Voltage regulation in power supplies
Timing circuits
Tuning circuits
Back-up power supplies

Question 40

When a voltage is connected to the capacitor _________ flow off one of the ________ plates and onto the ________ plates.

Answer 40

electrons
positive
negative

Question 41

The ____________ of a capacitor is defined as the _______ stored per unit potential difference change.

Answer 41

capacitance

charge

Question 42

Time constant is the time taken for a capacitor to discharge to _____ of its ______ charge.

Answer 42

0.37

initial

Question 43

The potential difference across a device is equal to the _____ _____ per unit ______ passing through the device.

Answer 43

work done

charge

Question 44

The electromotive force (emf) of a power supply is equal to the _______ supplied per unit _______ by the power supply.

Answer 44

energy

charge

Question 45

1 volt is equivalent to?

Answer 45

1 joule per coloumb