Electricity
(problem solving)
Prepared by:
Edward A. Mirador
San Bartolome High School
1. How much electrical energy is
used up in 2 hours by a 220 V
electric stove whose power rating
is 3 kW?
A – 3 kWh
B – 6 kWh
C – 440 kWh
D – 660 kWh
Correct !
E=Pxt
Congratulations
2. What is the total amount of
electrical energy consumed by
three 100W lamps and five 50W
lamps if these are used for 30 days
at an average of five hours daily?
A – 0.825 kWh
B – 8.25 kWh
C – 82.5 kWh
D – 825.0 kWh
Correct !
E=Pxt
300W x 150h = 45kW
250W x 150h = 37.5kW
+
82.5kW
Congratulations
3. How much current is in the
filament of a 100 W lamp
connected to a 220 V line?
A – 0.45 A
B – 2.2 A
C – 4.5 A
D – 22.0 A
Correct !
I=P/V
Congratulations
4. An electric meter showed an
increase in reading of 8 kWh after a
flat iron was used. About how many
hours was it used if it carried a 5 A
current from a 220 V line?
A–1
B–4
C–7
D – 40
Correct !
P=VxI
t =E/P
Congratulations
5. Fifty identical Christmas lights are
connected in series and plugged into a
220V line. Neglecting wire resistance,
what is the voltage across each bulb?
A – 2.2 V
B – 4.4 V
C – 110 V
D – 220 V
Correct !
.
Vtotal = V1 + V2 + V3+…+ Vn
n = number of loads
Since R is identical so as the V across
Therefore V = Vtotal / n
Congratulations
6. Which of the following correctly
ranks the equivalent resistance of the
three 100 resistors arranged as
shown below from greatest to least
value??
A – 2-1-4-3
B – 2-3-1-4
C – 2-3-4-1
D – 2-4-1-3
Correct !
.
1. RT = 1/3 R
2. RT = 3 R
3. RT = 3/2 R
4. RT = 2/3 R
Congratulations
Sorry
That was the wrong answer