Advertisements
Advertisements
प्रश्न
Calculate the current through a 60 W lamp rated for 250 V. If the line voltage falls to 200 V, how is the power consumed by the bulb affected?
Advertisements
उत्तर
Given,
Power (P) = 60 W
Voltage (V) = 250 V
We know that,
Power (P) = VI
Substituting the values in the formula above, we get,
`60 = 250 xx "I"`
`=> "I" = 60/250`
`=> "I" = 0.24 A`
Hence, current through the lamp = 0.24 A
Power consumed when voltage is 200 V = ?
Resistance of lamp (R) = `"V"^2/"P"`
Substituting the values in the formula, we get,
R = `250^2/60`
⇒ R = 1041.6 Ω
From relation,
P = `"V"^2/"R"`
Substituting the values in the formula, we get,
P = `200^2/1041.6`
⇒ P = 38.4 W
Hence, power consumed reduces to 38.4 W.
APPEARS IN
संबंधित प्रश्न
What is the meaning of the symbol kWh? Which quantity does it represent?
An electric kettle connected to the 230 V mains supply draws a current of 10 A. Calculate:
(a) the power of the kettle.
(b) the energy transferred in 1 minute.
A 2 kWh heater, a 200 W TV and three 100 W lamps are all switched on from 6 p.m. to 10 p.m. What is the total cost at Rs 5.50 per kWh?
Tick(✓) the correct choice in the following:
In the circuit shown in the following fig, the e.m.f. of the cell is 4 volts, the current
flowing through the resistor is
Name two common material used for heating elements.
Name a metal that is used as an electron emitter. Give one reason for using this metal.
A family uses a light bulb of 100W, a fan of 100W, and a heater of 1000W, each for 8 hours a day. If the cost of electricity is Rs. 2 per unit, what is the expenditure to the family per day, on electricity?
A. bulb is rated at 100W, 250V and another one at 60W, 250V. What is the current flowing in the circuit if the two bulbs are put in series across a 220 V mains supply?
A fuse is rated 5 A. Can it be used with a geyser rated 1540 W, 220 V Write Yes or No. Give supporting calculations to justify your answer.
