Generation Of Electricity 1

Diagram 24 shows an electrical energy transmission and distribution system from a power station to industrial, town and residential areas.

Diagram 24 The decreases of voltage are done A

because it depends on different values of current

B

because the main substation can accept only 33 kV

C

due to the different requirements of energy by the industries and the residential areas

D

to ensure the step-up transformer and step-down transformer function very effectively PMR 2007

2

Diagram 21 shows three types of generators, P, Q and R.

Diagram 21 What are generators, P, Q and R? P

Q

R

A

Gas turbine

Hydroelectric

Thermal

B

Hydroelectric

Gas turbine

Thermal

C

Hydroelectric

Thermal

Gas turbine

D

Thermal

Gas turbine

Hydroelectric PMR 2008

3

An electrical appliance labelled 240 V, 750 W is used for 60 hours. What is the cost of the electrical energy used if the cost per unit is 30 sen? A

RM 3.60

B

RM 4.32

C

RM 6.75

D

RM13.50

2

PMR 2008 4

An air conditioner is marked 240 V, 3 000 W. Calculate the current flowing through the air conditioner. A

0.08 A

B

1.08 A

C

12.5 A

D

13.5 A PMR 2008

3

Paper 2 1

Figure 1.1 shows a 3-pin plug. (PMR 2005)

Figure 1.1 (a) On Figure 1.1, label one wire using the following words:

Neutral wire

Earth wire

Live wire (1 mark)

(b) Figure 1.2 shows a connection of two electrical appliances to their plug.

Figure 1.2 Explain the advantage of the connection of the electrical appliance to the 3-pin plug, rather than to the 2-pin plug. ............................................................................................................................... ...............................................................................................................................

4

(2 marks) (c) Calculate the current flow in an iron labelled 2 000 watts and 240 volts. Suggest the suitable fuse that can be used. Use the following formula: Current = Power Voltage

The suitable fuse can be used is .......................................................................A (3 marks)

5

Generation of Electricity Paper 1 1. C 2. C 3. D 4. C Paper 2 No. 1

Answer a) Earth wire Neutral wire Live wire

b) The 3-pin plug has fuse to cut of the excessive current flow. c) Current = Power Voltage = 2000 240 = 8.3 A The suitable fuse can be used is 10 A.

6

T3 bab 8