January 2018

Question 1

Thermistor is

Answer 1

Temperature dependant and cuts out at set temperature.

Symbol is rectangle with hockey stick

Question 2

Capacitor is

Answer 2

2 electrodes (pos + neg -)
2 metal plates insulated by dielectric.
Store charge between plates.
Measured in Ferands F

Question 3

Diode is?

Answer 3

A semiconductor.
Has an anode and a cathode.
Can be light emitting (LED)

Symbol is cross with triangle

Question 4

Symbol for LED?

Answer 4

Cross with triangle and 2 arrows on right side

Question 5

Diac is for?

Answer 5

Alternating current

Symbol is vertical line but up and down arrows in the middle.

Question 6

Triac is?

Answer 6

Similar to Diac but has a trigger or (Gate).

Symbol is vertical line, in down arrows in the middle but also has A2 at top and A1 at bottom and the left arrow pointing up is indicated as the Gate.

Question 7

Thyristor is?

Answer 7

A controlled Diode
Has a trigger(also Gate)

Symbol is Cross with triangle but top of triangle is the Gate

Question 8

An Invertor does what?

Answer 8

Converts DC to AC

Opposite of Rectifyier.

Question 9

What do Transistors do?

Answer 9

Small current controls large current. Amplifier or switch.

NPN-circle with arrow going out ,at bottom right.
PNP-circle with arrow going in , at bottom right.

Question 10

Security Alarms are ,”Normally”?

Answer 10

“Closed”

Question 11

Stages of Electricity Production are?

Answer 11

Generation

Transmission

Distribution

Question 12

Fossil Fuel Generation of Electricity steps

Answer 12

1. Coal 2. Water 3.Heat to steam 4. Steam to turbine 5. Turbine turns generator 6. Electricity

Question 13

The Transmission stage , in the production of Electricity, is from where to where?

Answer 13

From Power Station to Substation (Load Centre)

Question 14

How many stages involved in Transmission of Electricity?

Answer 14

2

1. Transmit the voltage from Power Station after its been transformed up.
2. Decrease the voltage to usable values.

Question 15

In the Distribution of Electricity, state the voltages of Industry, commercial and Domestic voltages.

Answer 15

Industry- 33KV
Commercial-230V to 11KV
Domestic-230V

Question 16

State the voltages in the 3 stages in The Production of Electricity.

Answer 16

Generation - 25KV

Transmission - 132KV,275KV, and 400KV (Today it’s 400KV)

Distribution - 33KV, 11KV 400V then 230V

Question 17

What are the 4 types of Power Stations?

Answer 17

COAL

OIL

NUCLEAR

HYDRO

Question 18

What are Transformers used for?

Answer 18

To step up or step down voltage.

Question 19

Transformers have , how many parts?

Answer 19

2

Primary and Secondary