Intervention Material in Science (Energy Usage)

1. An Intervention Material in Science 9

2. JOHN FLORENTINO E. ECHON
Proponent, Taltal National High School
LENIE N. ELAMPARO, Ed. D.
Principal II, Taltal National High School
A Strategic Intervention Material
in Science 9
APRIL 2016

3. Least Mastered Learning
Competency
• Calculating energy usage
JOHN FLORENTINO E. ECHON, TNHS

4. Guide
Card
JOHN FLORENTINO E. ECHON, TNHS

5. Calculating Energy Use
• Do you know that you can calculate your electric bill? But before that, let us know the basis for calculating
your electric bill. One of the factors to be consider is the power rating of your appliance. By the way, what
is power? You learned in Grade 8 the three electrical basic quantities which are current, voltage, and
resistance. Multiplying the voltage and current is equal to power. For instance, the power rating of an
appliance depends on both the voltage and current.
The formula in finding power (in watts) is written below.
P = VI
where: P = Power (Watts)
V = Voltage (Volts)
I = Current (Amperes)
For example, an electric fan draws 5-A current from a 220-V outlet, its powerinput is 1,100 W. For
one appliance, the power rating is large in number, so the unit used for combined power rating in
a household is in kilowatt (kW) which is equal to 1000 watts.
JOHN FLORENTINO E. ECHON, TNHS

6. All of the appliances in a household may have a combined power rating, that is why, energy is usually computed based
on the time of usage of the appliances. To get the total energy used by an appliance in an hour, multiply the power
consumption by the one hour as in the formula below:
E = Pt
where: E = Energy used (kWh)
P = Power, (W)
T = Time (s)
The unit of measurement for energy usage is kilowatt-hour (kWh) which is one kilowatt of power for a period of one
hour. To find how much energy you used in one month, your last month’s reading is subtracted from the total.
2. How much does it cost to operate a 400 W television for 8
hours if electrical energy costs 6.88 pesos per kWh (includes
both generation and distribution
charges - Meralco rate as of January, 2014) ?
Find: cost to operate
E = Pt
= (0.400 kW)(8 h)
E = 3.2 kWh
Cost = (3.2 kWh) (6.88 pesos/kWh)
= 22.02 pesos
2. How much does it cost to operate a 400 W television for 8 hours if
electrical energy costs 6.88 pesos per kWh (includes both generation
and distribution
charges - Meralco rate as of January, 2014) ?
Find: cost to operate
E = Pt
= (0.400 kW)(8 h)
E = 3.2 kWh
Cost = (3.2 kWh) (6.88 pesos/kWh)
= 22.02 pesos
SAMPLE PROBLEMS
JOHN FLORENTINO E. ECHON, TNHS

7. Activity
Card
JOHN FLORENTINO E. ECHON, TNHS

8. Complete
me!
Appliances Kilowatts (kW) # of hours Energy Usage
Cost
(6.88
pesos/kWh)
Television 10 18
Refrigerator 15 10
Flat Iron 3 9
Electric fan 5 15
Washing
Machine
5 17
JOHN FLORENTINO E. ECHON, TNHS

9. assessment
Card
JOHN FLORENTINO E. ECHON, TNHS

10. Calculate!
1. Last month, Ms. Alcantara’s electric meter reads 8765
kWh. How much will she pay for power generation if
the charge of electric company per kWh is 6.88 pesos
and her electric meter reads 9975 this month?
2. Jaypeth paid ₱1250.00 for electric bill. How much
energy (in kWh) is consumed if the electric company
charges ₱6.88/kWh?
JOHN FLORENTINO E. ECHON, TNHS

11. enrichment
Card
JOHN FLORENTINO E. ECHON, TNHS

12. • If a 100 W light bulb is lit for 8 hours each day for 20 days in a month.
How many kilowatt-hours will the bulb consume?
• Give atleast five energy saving tips for each of the following appliances below:
1. Television
2. Refrigerator
3. Washing Machine
JOHN FLORENTINO E. ECHON, TNHS

13. reference
Card
JOHN FLORENTINO E. ECHON, TNHS

14. Science 9 LM (2014). Last Quarter. Electricity and
Magnetism. pp 14-16
JOHN FLORENTINO E. ECHON, TNHS