Page 136 - Physics Form 5 KSSM_Neat

Solving Problems Involving Electrical Energy and Power in Daily Life

Example 1
LET’S ANSWER
LET’S ANSWER
Figure 3.35 shows a circuit that is supplied with 6 V
a 6 V battery to light up a lamp. If the current
is 0.7 A, what is the amount of electrical energy
used to light up the lamp for one minute?

Solution Figure 3.35 https://bit.
ly/3jlXjWq

Step 1: Step 2: Step 3: Step 4:
Identify the Identify the Identify the formula Solve the problem
problem information given that can be used numerically

1 Total electrical energy, E 3 E = VQ
Q = It
2 Potential difference, V = 6 V Therefore, E = VIt
Current, I = 0.7 A
Time, t = 1 × 60 s 4 E = 6 × 0.7 × 60

= 252 J
KEMENTERIAN PENDIDIKAN MALAYSIA
= 60 s

Example 2 Info
Scan the QR code for tips on
A fluorescent lamp is labelled 240 V, 32 W. how to use formulae to solve
Calculate: problems involving electrical
(a) the lamp resistance energy and power.
(b) the current flowing through the lamp under
normal conditions https://bit.
(c) the electrical energy that is supplied for three hours in kJ ly/3lxmt6G

Solution

(a) Electrical power (b) Electrical power (c) Electrical power
required, P = 32 W required, P = 32 W required, P = 32 W
Potential difference across Potential difference across Time, t = 3 × 60 × 60
the lamp, V = 240 V the lamp, V = 240 V = 10 800 s
Resistance, R = V 2 Current, I = P Electrical energy,
P V E = Pt
= 240 2 = 32 = 32 × 10 800
32 240
= 1 800 W = 0.13 A = 345 600 J
= 345.6 kJ

126 LS 3.4.3