Page 135 - Physics Form 5 KSSM_Neat

The Relationship between Power (P), Voltage (V) and Current (I) CHAPTER 3
Have you ever seen a label as shown in
Photograph 3.7? The label displays the Electricity
voltage and electrical power required to
operate the electrical appliance.

Based on the label in Photograph 3.7, the
KEMENTERIAN PENDIDIKAN MALAYSIA
electric rice cooker will use 700 J of electrical energy
in one second when a voltage of 240 V is supplied.
This information can be used to calculate the amount
of electrical energy that is used over a period of time.

Photograph 3.7 Power rating label on an electric rice cooker

Electrical energy used
Electrical power =
Time taken
P = E
t
and electrical energy, E = VIt

Therefore, the relationship between P, V and I can be Info GALLERY
derived as:
The voltage labelled on an
P = VIt electrical appliance is the working
t voltage. The working voltage is
P = VI the potential difference required
for an electrical appliance to
From Ohm's Law, V = IR, two other equations for operate under normal conditions.
When an electrical appliance is
electrical power, P can be obtained as follows: operating at the working voltage,
the electrical power used is as
V
2
1 P = V ( ), then P = V stated in the label.
R R
2 P = (IR)I, then P = I R
2

–1
The S.I. unit for electrical power, P is watt (W) or J s .

LS 3.4.2 125