Advertisements
Advertisements
Question
What is the commercial unit of electrical energy? Represent it in terms of joules.
Advertisements
Solution
The commercial unit of electrical energy is Kilowatt hour (kWh)
1 kWh = 1000 W × 1 h
`1 "kWh" = 1000 "J"/"s" × 3600 "s"`
1 kWh = 3.6 × 106 J
APPEARS IN
RELATED QUESTIONS
What determines the rate at which energy is delivered by a current?
An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.
Which of the following terms does not represent electrical power in a circuit?
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
An electric fan runs from the 230 V mains. The current flowing through it is 0.4 A. At what rate is electrical energy transferred by the fan?
Which of the following is likely to be the correct wattage for an electric iron used in our homes?
(a) 60 W
(b) 250 W
(c) 850 W
(d) 2000 W
Explain why, filament type electric bulbs are not power efficient.
Name the S.I. unit of electrical energy. How is it related to Wh?
An electric bulb is rated ‘100 W, 250 V’. What information does this convey?
What is the current I in the given circuit (Fig. )?
What is electric power? State and define its S.I. unit.
In an electric radiator or room heater, state with reason, why the porcelain tube wound with a nichrome wire is placed between the pole and principal focus of the parabolic concave reflector.
Name a metal that is used as an electron emitter. Give one reason for using this metal.
Give two precautious that you would take while putting off an electric switch.
An electric bulb is rated 240V-60W and is working at 100% efficiency.
(i) Calculate the resistance of bulb.
(ii) (a) Draw the circuit diagram.
(b) What is the rate of conversion of energy in each bulb?
(c) Total power used by the bulbs.
Find the energy released by a current of 0.25 amperes flowing through a heater for 5 minutes. The p.d. is 230 V.
A room has AC run for 5 hours a day at a voltage of 220V. The wiring of the room consists of Cu of 1 mm radius and a length of 10 m. Power consumption per day is 10 commercial units. What fraction of it goes in the joule heating in wires? What would happen if the wiring is made of aluminium of the same dimensions?
`[ρ_(Cu) = 1.7 xx 10_(Ωm)^-8, ρ_(Al) = 2.7 xx 10^-8 Ωm]`
