Page 114 - Physics Form 5 KSSM_Neat

Example 1

LET’S ANSWER
Three resistors are arranged in series and in parallel as shown in Figure 3.13. LET’S ANSWER
The resistance for R , R and R are 2 W, 4 W and 12 W respectively.
1 2 3
6 V
KEMENTERIAN PENDIDIKAN MALAYSIA
R 2
A A https://bit.
1 R 2
1 ly/32J6R7B
R 3
A
3
Figure 3.13
When the switch is closed, calculate:
(a) the effective resistance, R
(b) the current flowing through the 2 W resistor and the potential difference across it
(c) the current flowing through the 4 W and 12 W resistors and the potential difference across
them respectively
Solution

(a) R
6 V 4 6 V
R 2
A R A 2 A
1 1 1 R 1 R 4
R 3
A 2 Ω
3
Total resistance in the parallel circuit, Thus, the effective resistance in the complete circuit,
1 = + 1 R = R + R 4
1
1
R R R = 2 + 3
4 2 3 = 5 W
= 1 + 1
4 12
4
=
12
12
R =
4 4
= 3 W
(b) Total current flowing in the circuit,
I = V 6 V
R I R
I = 6 A 2
5 2
= 1.2 A A 1 I R I 2 V 2
1 1
I = I
1 V I
Thus, the potential difference for V = I R 1 3 A R 3
1
1
1
V = 1.2 (2) 3
1
= 2.4 V V 3
V
104 LS 3.2.2