Power

Q. The rate of doing work is called.

1. power
2. energy
3. force

Q.

In the given arrangement, if we replace the copper plate connected to the negative terminal of the battery with a carbon rod, which of the following happens?

1. The mass of the copper plate increases.

2. Copper gets coated on the carbon rod.

3. Carbon gets coated on the copper rod.

4. The mass of the carbon rod decreases.

Q. The work done by the heart is $1J$ per beat. If it beats $72$ times in $1$ minute, then the power of heart is .

1. $1.2W$
2. $2.4W$
3. $3.6W$

Q.

How is hydrogen prepared from water using the method of electrolysis?

Q.

In LEDs, the longer lead is always connected to _______ terminal

1. negative

2. neutral

3. either negative or positive

4. positive

Q.

State the purpose of kWh meter.

Q. 1 watt is defined as

1. work done at the rate of 1 joule-second.
2. 1 joule of work done in an hour.
3. 1 joule of work done in 60 seconds.
4. 1 joule of work done in 1 second

Q.

When electric current is passed through an incandescent bulb, the bulb gives light. Identify the proper reason.

1. Magnetic effect of current

2. Heating effect of current

3. Electric effect of current

4. Chemical effect of current

Q.

Power spent by a body depends on the time for which it does work.

1. True

2. False

Q. A car accelerates from rest to $100m{s}^{-1}$ in ten seconds. If mass of the car is $50kg$, then the average power developed by the engine is:

1. $25kW$
2. $30kW$
3. $35kW$
4. $40kW$

Q.

Our body is a ________________ of electricity.

Q. An electric bulb of 50 W is used for 5 hours. Calculate the energy consumed by the bulb.​

1. $9\times {10}^{6}J$
2. 9 kJ​
3. 90 kJ​
4. $9\times {10}^{5}J$

Q.

The power of a motor pump in a house is $\text{20 W}$. How much water per minute can the pump raise to a height of $\text{10 m}$?
Take acceleration due to gravity $g=10m{s}^{-2}$

1. 6 kg

2. 20 kg

3. 12 kg

4. 24 kg

Q. The power of a motor pump is $20W$. The work done by pump in 1 minute is $x$ then $\frac{x}{100}$ = ___

1. 12

Q. Each time the heart beats, it requires $5J$ of energy. If it beats 72 times in one minute, then the power consumed by the heart is:

1. $3W$
2. $6W$
3. $3W$
4. $12W$

Q.

Arun is travelling with his friends in a car. The car suddenly stops due to some problem in the engine. If Arun and his friends apply a force of 1000 N to drag the car to the nearest garage that is 1.2 km from that place in 20 minutes, determine the total power spent by him.

1. 2000 W

2. 3000 W

3. 1000 W

4. 500 W

Q.

A pump raises water by spending $4\times {10}^5$ J of energy in 10 s. Find the power of pump.

Q.

A car is moving with an initial velocity of $10m{s}^{-1}$ with an acceleration of $5m{s}^{-2}$ for a time interval of 10 seconds. Mass of the car is 20 kg, find average power of the car.

1. 3500 W

2. 7000 W

3. 2000 W

4. 5000 W

Q.

If the work done on a body for two different time interval i.e., $\text{20s}$ and $\text{40s}$ is the same, then what is the ratio of the power?

1. 2:1

2. 1:2

3. 1:4

4. 4:1

Q.

How can you make distilled water conducting?

Q. In a hydroelectric power plant, moving water is used for driving the wheels of a turbine to generate electricity. If the change in the kinetic energy of turbine is $3600J$ in two minutes, then the power generated will be:

1. $60W$
2. $180W$
3. $30W$
4. $100W$

Q. The commercial unit of energy is $kWh$. It is equal to joules.

1. $1.3\times {10}^6$​
2. $3\times {10}^6$​
3. $3.6\times {10}^6$​
4. $6\times {10}^6$​

Q. A particle of mass $1kg$ was sliding with a velocity of $10m{s}^{-1}$ on a rough floor. It comes to rest after $5s$. The rate at which floor warms up is:

1. $5W$
2. $10W$
3. $5W$
4. $20W$

Q. Which of the following statements are correct about power?

1. It is the rate of change of momentum.
2. It is the rate of change of force.
3. It is the rate of doing work.
4. The S.I. unit of power is watt.

Q.

Which of the following units is/are used to describe power?

1. watt

2. pascal

3. horse-power

4. $J{s}^{-1}$

Q. Metals are good conductors of electricity because they have:

1. Excess positive charges
2. Free electrons
3. Neutrons
4. A tight molecular packing

Q.

$\text{50kJ}$ of energy is consumed in $\text{2.5s}$. Find the power in a unit of horse power.

1. 28.6 hp

2. 13.4 hp

3. 14.3 hp

4. 26.8 hp

Q. Two cities are 150 km apart. Electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volt and the average resistance per km is $0.5\Omega$. The power loss in the wire is

1. 19.2 W
2. 19.2 kW
3. 19.2 J
4. 12.2 kW

Q.

How many joules are there in 1 kWh?

Q.

State True or False

Each time the heart beats, it requires 5 J of energy. If it beats 72 times in one minute then the power consumed by the heart is 360 W.

1. 4W

2. 2W