Advertisements
Advertisements
प्रश्न
Two bulbs are rated: bulb A 100W, 120 V bulb B 10 W, 120 V. If both are connected across a 120V supply, which bulb will consume more energy, When in parallel? Also calculate the current through each bulb in the above cases.
Advertisements
उत्तर
In the case of bulb A, Power: P = `"V"^2/"R"_"A"`
RA = `"V"^2/"P" = (120 xx 120)/100` = 144 Ω
i.e., Resistance (RA ) of bulb, A = 144 Ω
Similarly resistance RB of bulb, B = `"V"^2/"P"`
`= (120 xx 120)/10 = 1440` Ω
When the bulb are connected in Parallel:
Voltage is the same (120 V) across each bulb.
∴ The current in bulb A or IA = `"V"/"R"_"A" = 120/144 = 0.83` A
∴ The current in bulb B or IB `= 120/1440` = 0.083 A
Hence, power consumed in bulb A = PA = `"V"^2/"R"_"A" = (120 xx 120)/144`
= 100 W
and power consumed in bulb B = PB = `"V"^2/"R"_"B"`
`= (120 xx 120)/1440 = 10 "W"`
Hence, bulb A (100W, 120 V) consumes more energy then bulb B, when both are connected in parallel.
संबंधित प्रश्न
What is meant by "electric power"?
State whether an electric heater will consume more electrical energy or less electrical energy per second when the length of its heating element is reduced. Give reasons for your answer.
An electric bulb is rated ‘100 W, 250 V’. What information does this convey?
A potential difference of 6 V is applied across a 3 Ω resistor. What is the current flowinq throuqh the circuit?
What would happen and why, to an electric bulb when it is connected across a supply of voltage (i) lower (ii) higher than its proper rating?
State relative advantages and disadvantages of ring system of wiring over the tree system.
A battery of e.m.f. 12V and internal resistance 1.6 Ω is connected to two resistors of 4Ω and 6Ω connected in parallel. Calculate:
(i) the current drawn from the battery,
(ii) the power dissipated in each resistor,
(ii)the total power supplied by the battery.
A 100-watt electric bulb is used for 5 hours daily and four 60 watt bulbs are used for 5 hours daily. Calculate the energy consumed (in kWh) in the month of January.
A student wants to use an electric heater, an electric bulb and an electric fan simultaneously.
How should these gadgets be connected with the mains? Justify your answer giving three reasons.
An overhead tank of capacity 10 k litre is kept at the top of building 15 m high. Water falls in tank with speed 5`sqrt2` m/s. Water level is at a depth 5 m below ground. The tank is to be filled in `1/2` hr. If efficiency of pump is 67.5% electric power used is ______ W.
