Chua Cong Yang | Khoo Yihan | Park Seong Jin
4S2 Inertia
Physics: PBL Wired Up!
Appliance
Shaver
Wattage/W
Time daily/h
Room
15
5/60
Bathroom
Water Heater
2552
40/60
Bathroom
Hair Dryer
1200
5/60
Bedroom Main
10
120/60
Bedroom Main
110
20/60
Bedroom 2
1900
600/60
3 Bedrooms
350
100/60
Kitchen
Iron
1000
30/60
Kitchen
Toaster
1550
5/60
Kitchen
Refrigerator
1725
24
Kitchen
Radio
Television Set
Air Conditioning
Washing
Machine
Appliance
Wattage/W
Time daily/h
Room
Vacuum Cleaner
630
15/60
Living Room
Laptop
240
120/60
Living Room
Television Set
(Small)
70
60/60
Living Room
Massage Chair
50
30/60
Living Room
940
19
Lights
All rooms
Energy Used (in kWh)
15 5 2552 40 1200 5
10 120 110 20
=
( )
( )
( )
(
)
( )
1000 60 1000 60 1000 60 1000 60 1000 60
1900 600
350 100 1000 30 1550 5 1725
(
)
(
)
( )
( )
(24) 
1000 60 1000 60 1000 60 1000 60 1000
630 15
240 120
70 60
50 30
940

( )
(
)
( )
( )
(19)
1000 60 1000 60 1000 60 1000 60 1000
 253.342583 kWh
=253.3 kWh
Given each power socket draws a maximum of
15A current before circuit trips
Room
No. of Sockets Max
Current/A
No. of Sockets Current used
used daily
daily/A
Living Room
8
120
4
60
Main Bedroom
4
60
3
45
Bedroom 2
4
60
2
60
Bedroom 3
4
60
1
15
Kitchen
4
60
3
45
2 Bathrooms
2
30
1
15
TOTAL
240
Lighting in each room is
aligned in parallel.
Each bulb is 10W.
W
I (in amps) 
(in watts/volts)
E
10
I
 0.5599 A  0.56 A (2 s.f.)
940
(19)
1000
Room
No. of lights
Current used/A
Living Room
3
1.68
Main Bedroom
1
0.56
Bedroom 2
1
0.56
Bedroom 3
1
0.56
Kitchen
2
1.12
2 Bathrooms
2
1.12
TOTAL
5.6



Built in RCD (Residual Current Device) that
will trip the whole main circuit in the event of
a current overload.
Earth wires built in for each power socket.
The mains are fitted with an Earth Line Circuit
Breaker to prevent electric shocks should the
live or neutral wires be in contact with
conductors in the appliances.
Lighting placed in parallel to ensure that if
one bulb blows, the rest still works.

Check for energy-efficient appliances, with
labels as:
◦ To minimize electricity consumption (low wattage
appliances).

Set your clothes washer to the warm or cold
water setting, not hot.
◦ Switching from hot to warm for two loads per week can
save nearly 500 pounds of CO2 per year if you have an
electric water heater, or 150 pounds for a gas heater.

Turn down your water heater thermostat.
◦ Thermostats are often set to 140 degrees F when 120 is
usually fine.
◦ Each 10 degree reduction saves 600 pounds of CO2 per
year for an electric water heater, or 440 pounds for a gas
heater.

Weatherize your home using caulk and
weather stripping.
◦ Plug air leaks around doors and windows.
◦ Caulking* costs less than $1 per window, and
weather stripping is under $10 per door.
◦ These steps can save up to 1100 pounds of CO2
per year for a typical home.
◦ * Caulking is one of several different processes to seal joints or seams in
various structures and certain types of piping to cut energy costs in keeping
rooms warm/cold.



Usage of electricity by the household is
consistent on a daily basis
No new appliances are added or removed
from this circuit design
All the lighting used in the house is identical
and of the same wattage.

How do we apply our new knowledge to solve the
problem?
◦ Seeking ways to get a design that minimizes cost.
◦ No compromise on safety.

What evidence is required to support our
solution?
◦ Mathematical calculations to show cost-effectiveness.

Have we address all the concerns that surface in
the problem?
◦ Troubleshoot any possible flaws in the design.


http://en.wikipedia.org/wiki/Caulking
http://www.powerscorecard.org/reduce_ener
gy.cfm
◦ Last accessed on 14th April 2012
◦ [Online] Resource.
4S2 | Inertia