Electricity Worksheet-9
Answer Key:
Let the third resistance be x Ω. Since 10 Ω, 12 Ω or x Ω are in parallel,
or
Or or x = 15 Ω
Since three pieces of (80/3) Ω are in parallel, the resultant resistance of the combination,
As R_{1} (= 6 Ω) and 3 Ω (in arm AB) are in parallel, effective resistance between the points A and B, i.e.,
(ii) since the effective resistance between point A and B (i.e., 2 Ω) and in the arm AC (= 3 Ω) and arm BD (= 3 Ω) are in series, effective resistance between the points C and D = 2 + 3 + 3 = 8 Ω
Power of the bulb, P = 100 W
As
Electric energy consumed by 1 bulb in 4 hours, i.e.,
W = P t = 100 W × 4h = 400 Wh
Electric energy consumed by 5 bulb in 4 hours
= 5 × 400 Wh = 2000 Wh = 2kWh = 2 unit
Cost of 2 units of electric energy = 2 × 50 paise = Re.1
Time for which the bulb is lighted, t = 4 hour
(i) power of the bulb, P = VI = 2.5 × 0.75 = 1.875 watt
(ii) resistance of the bulb, ohm
(iii) energy consumed by the bulb in 4 hour i.e.
W = Pt = 1.875 × 4 = 7.5 Wh = 7.5 W × 3600 s
= 27000 J