Advertisements
Advertisements
Question
Calculate the current through a 60 W lamp rated 250 V. If the line voltage falls to 200 V, how is power consumed by the bulb affected?
Advertisements
Solution
Given ,
Power P = 60 W
Voltage , V = 250 V
As Power , P = VI
I = `60/250 = 0.24 "A"`
Resistance of bulb R = `"V"^2/"P" = 250^2/60 = 1041.6 Omega`
Now if voltage falls to 200 V , power consumed will be
P = `"V"^2/"R" = 200^2/1041.6 = 38.4 "W"`
RELATED QUESTIONS
Which of the two is connected in series : ammeter or voltmeter?
How many electrons are flowing per second past a point in a circuit in which there is a current of 5 amp?
(a) With the help of a circuit diagram, obtain the relation for the equivalent resistance of two resistances connected in parallel.
(b) In the circuit diagram shown below, find:
(i) Total resistance.
(ii) Current shown by the ammeter A
You can given one hundred 1 Ω resistors. What is the smallest and largest resistance you can make in a circuit using these?
How do you think the brightness of two lamps arranged in parallel compares with the brightness of two lamps arranged in series (both arrangements having one cell)?
A wire of length 5 m has a resistance of 2.0 Ω calculate:
(a) the resistance of wire of length 1 m
(b) the equivalent resistance if two such wires each of length 2 m are joined in parallel.
(c) the resistance of 1 m length of wire of same material but of half diameter.
A battery of e.m.f. 15 V and internal resistance 3 ohm is connected to two resistors of resistance 3 ohm and 6 ohm in series. Find:
(i) The current through the battery,
(ii) The p.d. between the terminals of the battery.
A current of 0.2 A flows through a wire whose ends are at a potential difference of 15 V. Calculate:
(i) The resistance of the wire, and
(ii) The heat energy produced in 1 minute.
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
1020 electrons, each having a charge of 1.6 x 10-19 C, flows in a circuit V is 0.1s. What is the current in ampere?
