Advertisements
Advertisements
Question
What is meant by "electric power"?
Advertisements
Solution
The energy required per unit of time is called electrical power.
RELATED QUESTIONS
If a bulb of 60W is connected across a source of 220V, find the current drawn by it.
An electric lamp is labelled 12 V, 36 W. This indicates that it should be used with a 12 V supply. What other information does the label provide?
An electric motor takes 5 amperes current form a 220 volt supply line. Calculate the power of the motor and electric energy consumed by it in 2 hours.
The SI unit of energy is :
(a) joule
(b) coulomb
(c) watt
(d) ohm-metre
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.
In a filament type light bulb, most of the electric power consumed appears as:
(a) visible light
(b) infra-red-rays
(c) ultraviolet rays
(d) fluorescent light
Electrical power P is given by the expression P = (Q × V) ÷ time. What do the symbols Q and V represent?

The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.
Which cable, one rated 15A and the other rated 5A will be thicker? Give a reason.
Name three main characteristics of an heating element.
State two advantages of filling an inert gas in an evacuated electric filament lamp.
What is the order of current drawn by appliances connected to the ‘power circuit’ of a household?
You are required to connect a bulb, a fan and a socket outlet to the mains in one set A and an air-conditioner and a refrigerator to the mains in other set B. Will you recommend the wire of same thickness and same insulation in both? explain your answer.
How is the amount of heat produced calculated due to the passage of current in a metallic conductor? Derive an expression for it.
State other bigger units of electric power and express them in watt.
An Electric bulb is marked 100 W, 230 V. What how long would this lamp take to consume one unit of electricity?
The following table gives the electrical appliances used, their power and the average time for which they are used each day in a home. Estimate the monthly electricity bill if the rate is 60 paise per unit.
| Sr.no. | Name | Nos. | Power rating | Time/day |
| 1 | Bulb | 4 | 100 W | 7.5 hr |
| 2 | Fans | 2 | 50 W | 10 hr |
| 3 | T.V. | 1 | 100 W | 2 hr |
| 4 | Iron | 1 | 500 W | 1 hr |
| 5 | Electric stove | 1 | 750 W | 2 hr |
