In a domestic circuit five LED bulbs are arranged as shown. The source voltage is 220 V and the power rating…
In a domestic circuit five LED bulbs are arranged as shown. The source voltage is 220 V and the power rating of each bulb is marked in the circuit diagram. Based on the following circuit diagram, answer the following questions :
(a) State what happens when
(i) key K1 is closed.
(ii) key K2 is closed. [1]
(b) Find the current drawn by the bulb B when it glows. [1]
(c) Calculate
(i) the resistance of bulb B, and
(ii) total resistance of the combination of four bulbs B, C, D and E. [2]
Solution
(a)
(i) Bulb A glows
(ii) Bulbs B, C, D and E glow
(b) P = V×I
11 = 55×I
I = 1/5 = 0.2 amp
(c)
(i) Resistance of bulb B, R = V/I = 55V/0.2A = 275 Ω
(alternative formula for calculation R = V²/P)
(ii) Total resistance of the series combination of four bulbs = 4×275 = 1100 Ω
