Power Questions

Power is the rate of doing work; it is the work done in unit time. The SI unit of power is Watt (W), which is joules per second (J/s). Power is a time-based quantity. Power is measured in newton metre per second.

Power = Work / time

P = W / t

Read more: Unit of power

Power is the rate at which energy is being used. It helps to analyse how fast work could be done. One horsepower is equivalent to approximately 745.7 Watts. Horsepower (hp) is equal to 33,000 foot-pounds per minute, or 6,600 inch-pounds per second. Power could change, so there are two ways to measure power.

• Instantaneous power: It is the power at any given moment.
• Average power: The total energy used divided by total time is the average of all the instantaneous powers.

We know that power is a scalar quantity. Other units of power include ergs per second (erg/s), foot-pounds per minute, dBm, a logarithmic measure relative to a reference of 1 milliwatt, calories per hour, BTU per hour (BTU/h), and tons of refrigeration. The formula gives average power:

Where,

ΔW is the amount of work performed

Δt is the time duration

The formula gives the instantaneous power in a component:

P(t)=I(t).V(t)

P(t) is the instantaneous power

V(t) is the component’s potential difference

I(t) is the power through it

If the component is a resistor with time-invariant voltage to current ratio, then:

P=I.V

Where

R=V/I

Radiant power is given by the formula:

Important Power Questions with Answers

1. Which among the following formulas is used to find power?

1. Power = Force + Velocity
2. Power = 2(Force – Velocity)
3. Power = Force / Velocity
4. Power = Force * Velocity

Answer: d) Power = Force * Velocity

Explanation: Power = Work/Time

Power = (Force.Displacement)/Time

Power = Force. (Displacement/Time)

Power = Force * Velocity

2. Fill in the blanks: Watt is the SI unit of _____

1. Luminosity
2. Temperature
3. Power
4. Angle

Answer: c) Power

Explanation: The SI unit of power is Watt (W).

3. One horsepower is equivalent to approximately _____

1. 845.7 watts
2. 745.7 watts
3. 645.7 watts
4. 545.7 watts

Answer: b) 745.7 watts

Explanation: Horsepower is used to define the power delivered by a machine, and it is approximately equal to 745.7 watts.

4. Define average power.

Average power is explained as the total energy consumed divided by the total time taken.

5. Choose Yes or No: Can the power of a motor be represented using horsepower?

1. YES
2. NO

Answer: a) YES

Explanation: Horsepower is used to define the power delivered by a machine or motor.

6. A watt is equivalent to _____

1. Joules
2. Newton/second
3. Joule/second
4. Newton

Answer: c) Joule/second

Explanation: Watt = Joule/second = 1 newton meter per second

7. One Gigawatt =

1. 1×10^5 W
2. 1×10^6 W
3. 1×10^6 W
4. 1×10^9 W

Answer: d) 1×10^9 W

8. Power is a _____

1. Vector
2. Scalar
3. Dimensionless
4. None of the options

Answer: b) Scalar

Explanation: Power is a scalar quantity since it has only magnitude and no direction.

9. The power at a given moment is known as _____

1. Average power
2. Instantaneous power
3. Unit of power
4. None of the options

Answer: b) Instantaneous power

Explanation: The power at any given moment of time gives instantaneous power.

10. 0.24 calories per second cal/sec =

1. 2W
2. 1W
3. 0W
4. 3W

Answer: b) 1W

Practice Questions

1. Define power.
2. List various units of power.
3. What is the formula to find the power?
4. Explain one kilowatt.
5. What is the formula to find the average power?

<b>See the video below to learn about the power in a detailed way.</b>