Electric Power

Q.

An electric bulb is rated $220V$ and $100W$. When it is operated on $110V$, what will be the power consumed?

Q.

Average power is defined as?

Q.

The potential difference across a conductor is doubled. Then the rate of generation of heat will

1. Be doubled

2. Be halved

3. Become one-fourth

4. Become four times

Q.

A wire 1 m long has a resistance of 1Ω. If it is uniformly stretched, so that its length increases by 25%, then its resistance will increase by:

1. 77.33%

2. 50%

3. 25%

4. 56.25%

Q.

A torch bulb Is rated at $3V$ and $600mA$. Calculate it’s power and resistance.

Q.

Household consumption of electrical energy is measured in the unit ______.

Q.

The coil of a heater is cut into two equal halves and only one of them is used in the heater. The ratio of the heat produced by this half of the coil to that produced by the original coil is,

1. $2:1$

2. $4:1$

3. $1:2$

4. $1:4$

Q.

In a premise, 5 bulbs each of 100 W, 2 fans each of 60 W, 2 A.Cs each of 1.5 kW are used for 5 h per day. Find:

(a) total power consumed per day,

(b) total power consumed in 30 days.

(c) total electric energy consumed in 30 days.

(d) the cost of electricity at the rate of Rs 6.25 per unit.

Q. Calculate the no. of 'units' of electricity consumed for a month for the following details of electrical components in a household. Consider all the given components are used for 10 hours a day. (Take 1 month = 30 days)

Home Appliance	Wattage
6 ceiling fans	60 W each
4 CFLs	15 W each

1. 12600
2. 1260
3. 126
4. 12.6

Q.

The energy dissipated in the L.C.R circuit in :

1. R only

2. L only

3. C only

4. All the above option.

Q.

If an electric bulb of 100 watt is lighted for 2 hours, how much electric energy would be consumed?

Q.

Why does a bulb when connected to a battery glows but not the wire connecting the two?

1. The bulb filament has lesser resistance.

2. More current flows through the bulb.

3. The bulb filament has more resistance.

4. Less current flows through the bulb.

Q.

An electric iron of power 1.5 kW is used for 30 minute.to press the clothes Calculate the electrical energy consumed in (a) kilowatt hour (b) joule.

Q. Question 15
The power of a motor pump is 2 kW. How much water per minute the pump can raise to a height of 10 m? (Given $g=10m{s}^{-2}$)

Q.

An electrical appliance is rated as 60 W -150 V.

(a) What do you understand by this statement?

(b) How much current will flow through the appliance when in use?

Q.

Two bulbs are marked as ‘A’ having rating 60W, 220V & ‘B’ having rating 100W, 220V. They are connected in parallel to a 220 V source. Which of the two will glow brighter?

1. Bulb A.

2. Both will glow with same brightness.

3. Bulb B.

4. Bulb A glows and B does not glow.

Q.

When a 0.5 kW heater operates for 20 minutes, the electrical energy consumed is equal to ___ kJ.

Q.

A source of potential difference V volt sends current I ampere in a circuit for time t second. Write expressions for

(a) electrical energy supplied by the source, and

(b) electrical power spent by the source.

Q.

Write an expression for calculating electrical power in terms of current and resistance.

Q.

A fuse of rating 5 A can be used for an electric heater is rated 2 kW, 220 V.

1. True

2. False

Q.

The time rate of doing work is called

1. Force

2. Kinetic energy

3. Power

4. Pressure

Q.

Give an example of a quantity which is dimensionless?

Q. Unit of electric power may also be expressed in

(A) volt ampere
(B) kilowatt hour
(C) watt second

Q.

Fill in the blanks:

(a) The unit in which we pay the cost of electricity is ___

(b) The electrical energy consumed in a house is measured by ___

(c) In a household electrical circuit, the appliances are connected in ___ with the mains.

(d) A switch is connected to the ___ wire.

(e) The red colour insulated wire in a cable is the ___ wire.

(f) One kilowatt hour is equal to ___ joule.

(g) A fuse wire should have low ___.

Q.

State a relation between electrical power, resistance and potential difference in a circuit.

Q.

(ampere² ohm) is the unit of which physical quantity?

1. Power

2. Work

3. Potential difference

4. Resistivity

Q.

An electric motor creates a tension of $9000N$ in a hoisting cable and reels it in at the rate of $2m{s}^{-1}$. The power of the electric motor is

1. $18kW$

2. $15kW$

3. $81W$

4. $225W$

Q.

When $1$coulomb of charge flows through any cross-section of a conductor in $1$ second then

Q.

Fifty lamps each of resistance $100ohm$ are connected in parallel across a $220V$main.

Find (a) the power consumed in watts, and (b) the cost of operating the lamps for $20$ hours at $10$ paise per $KWh$.

Q.

$1Kwh=\_\_\_\_\_\_\_\_J$