Power - Meaning, Unit, Formula, FAQs
Power in physics refers to the amount of work done or energy transferred per unit of time. It is expressed in watts (W) and a watt is the equivalent of one joule per second. Power measures, how fast the energy is used or converted to another form. In electrical systems, for e.g. power = voltage x current (in a charge-neutral case, what this really tells you is how much electrical energy is being consumed, or being pumped, per unit of time. Power is important in running the various types of equipment and machines we use in everyday life. Generally, the higher the power rating, the more work a device can do in less time.
JEE Main 2025: Physics Formula | Study Materials | High Scoring Topics | Preparation Guide
JEE Main 2025: Syllabus | Sample Papers | Mock Tests | PYQs | Study Plan 100 Days
NEET 2025: Syllabus | High Scoring Topics | PYQs
In this article, we are going to read about power and different types of power and also see some solved examples, which belong to the chapter work, energy, and Power, which is one of the important chapters in Class 11 physics. It is not only essential for board exams but also for competitive exams like the Joint Entrance Examination (JEE Main), National Eligibility Entrance Test (NEET), and other entrance exams such as SRMJEE, BITSAT, WBJEE, BCECE and more. Over the last ten years of the JEE Main exam (from 2013 to 2023), more than fifteen questions have been asked on this concept. And for NEET almost six questions were asked from this concept.
Let's read this entire article to gain an in-depth understanding of the concept of power.
Define Power
Power is defined as the rate at which work is done or energy is transferred.
Dimension- ML2T−3
Units - Watt or Joule/sec (in SI), Erg/sec (in CGS)
Average power
Pav=ΔwΔt=∫0tp⋅dt∫0tdt
Instantaneous power
P=dwdt=P=F→⋅v→
Where, F→→ force v→→ velocity
Power is expressed as the rate of change of kinetic Energy
P=dkdt
Where,
dk→ change in kinetic energy dt→ interval of time
i.e. power is equal to the scalar product of force with velocity
Recommended Topic Video
Solved Example Based on Power
Example 1: An engine of a car of mass m = 1000 Kg changes its velocity from 5 m/s to 25 m/s in 5 minutes. The power (in KW) of the engine is
1) 5
2) 2
3) 1
4) 4
Solution:
Power expressed as the rate of change of kinetic Energy -
Power = Work done / time = change in K.E / time
Power = dk/dt
P=12m[(25)2−(5)2]5×60=12×1000×6005×60=1000 WP=1KW
Hence, the answer is the option (3).
Example 2: A constant power-delivering machine has towed a box, which was initially at rest, along a horizontal straight line. The distance moved by the box in time 't' is proportional to :
1) t2/3
2) t
3) t3/2
4) t1/2
Solution:
Power delivered by machine is, P
Force acting on the machine, F
\text { As we know, } P=\vec{F} \cdot \vec{V}
As force and velocity have the same direction the angle between force and velocity is
So P=FV
or P=maV=mdVdtV
Given that the machine is delivering constant power.
So P=C (constant)
P=C
FV=C
MdVdtV=C
Integrating both sides, we get
V22∝tV∝t1/2dxdt∝t1/2 Again integrate both sides x∝t3/2
Hence, the answer is the option(3).
Example 3: Sand is being dropped from a stationary dropper at a rate of 0.5 kg−1 on a conveyor belt moving with a velocity of 5 ms−1. The power needed to keep the belt moving with the same velocity will be :
1) 1.25 W
2) 2.5 W
3) 6.25 W
4) 12.5 W
Solution:
The power needed to keep the belt moving with the same velocity will be
P=(dmdt)v2=(0.5)×25P=12.5 W
Hence, the answer is the option (4).
Example 4: A particle of mass M is moving in a circle of fixed radius R in such a way that its centripetal acceleration at time t is given by n2 R t2 where n is a constant. The power delivered to the particle by the force acting on it is:
1) Mn2R2t
2) MnR2t
3) MnR2t2
4) 12Mn2R2t2
Solution:
Centripetal acceleration, ac=n2rt2 where, ac=v2r
⇒v2r=n2rt2⇒v=nrt…
tangential acceleration, at=dvdt=nr…
Tangential force acting on the particle, F=Mat=Mnr
Power delivered, P=F→⋅v→=Fvcosθ
∴P=Fv=(Mnr)×nrt(∵θ=0∘)⟹P=Mn2r2t
Hence, the correct option is option 1.
Example 5: Sand is being dropped from a stationary dropper at a rate of 0.5 kg−1 on a conveyor belt moving with a velocity of 5 ms−1. The power needed to keep the belt moving with the same velocity will be :
1) 1.25 W
2) 2.5 W
3) 6.25 W
4) 12.5 W
Solution:
The power needed to keep the belt moving with the same velocity will be
P=(dmdt)v2=(0.5)×25P=12.5 W
Hence, the answer is the option (4).
Conclusion
Power in physics is the rate at which work is done or energy is transferred, measured in watts (W), which is equivalent to one joule per second. It can be calculated as the product of voltage and current in electrical systems and as the rate of change of kinetic energy in mechanical systems. Power is crucial for efficiently operating various equipment and machines. Understanding power is essential for exams like JEE Main and NEET, where multiple questions are often asked on this concept.
Frequently Asked Questions (FAQs)
The energy supplied by source in maintaining the flow of electric current is called electrical energy meanwhile the time rate at which electric energy is consumed by an electrical device is called electric power.
Power is a unit of measurement for the rate of energy transmission per unit of time. A scalar quantity is Power. In electrical engineering, Power refers to the rate at which electrical energy flows into or out of a given component.
It is defined as the rate at which work is completed. The watt is a unit of measurement.
Average power is the ratio of total effort or energy consumed to total time when a machine or person undertakes different quantities of work or utilizes energy at different periods of time.
Electric generators transform mechanical energy (the Power of motion) from an external source into electrical energy.
Also Read
21 Nov'24 04:30 PM
21 Nov'24 02:19 PM
20 Nov'24 07:40 PM
14 Nov'24 04:18 PM
12 Nov'24 10:07 PM
12 Nov'24 09:16 PM
11 Nov'24 07:26 PM
26 Sep'24 10:49 AM
26 Sep'24 10:21 AM
Articles
Questions related to
Hello,
The course fees for Solar Power Technology programs in Indian Rupees (INR) are approximately:
- Short certification programs : Rs. 16,600 to Rs. 1,24,500.
- Diploma or associate degree programs : Rs. 1,66,000 to Rs. 12,45,000.
- Bachelor's or master's degree programs : Rs. 8,30,000 to Rs. 24,90,000 or more per year.
For more info about such course, visit : https://www.careers360.com/courses-certifications/tcs-ion-digital-learning-hub-solar-power-technologies-course
Hope it helps !
To solve remainder problem you can use pattern recognition method,eulers therom,modular exponentiation, online calculator,etc.just simply simplify large powers into small ones,use pattern and cycle to reduce calculation and keep practicing to improve your skills.from the mod calculation the answer of this equation is 65.if you need calculation please specify in next question.
Hello,
To calculate the total power in the AM wave and power in each sideband, we can use the following formulas:
1. Total Power (Pt) = Carrier Power (Pc) x [1 + (μ^2)/2]
where μ is the modulation index (80% in this case)
1. Power in each sideband (Ps) = (μ^2/4) x Pc
Given:
Pc = 500 W (carrier power)
μ = 0.8 (modulation index)
Calculations:
1. Total Power (Pt) = 500 x [1 + (0.8^2)/2]
= 500 x [1 + 0.64/2]
= 500 x 1.32
= 660 W
2. Power in each sideband (Ps) = (0.8^2/4) x 500
= (0.64/4) x 500
= 0.16 x 500
= 80 W
So, the total power in the AM wave is 660 W, and the power in each sideband is 80 W.
Hope this helps,
Thank you
Applying for a job as airport ground staff with -5.00 power glasses and color blindness presents specific challenges but is not necessarily a barrier if you meet certain conditions. Here's how these factors could impact your job prospects:
Vision Requirements:
-
Eye Sight with Glasses: -5.00 power glasses indicate severe myopia (nearsightedness). Many airport ground staff roles require good vision for safety and operational efficiency. However, with corrective lenses, you may meet the visual acuity requirements, provided you pass the necessary eye tests. Ensure your glasses prescription is up-to-date and discuss your condition with prospective employers.
-
Color Blindness: Color blindness can be a significant factor depending on the specific duties of the role. Ground staff positions often require distinguishing between different colors for tasks like identifying signals, reading colored indicators, or managing baggage. Some roles might be more lenient if your color blindness does not interfere with critical job functions, but others might be more stringent.
Job Assessment:
-
Medical Examination: Most airport ground staff positions require passing a medical examination that assesses both vision and color discrimination. If your color blindness and vision can be managed with corrective lenses and do not impede job performance, you may still be considered.
-
Job Specifications: Review job descriptions carefully to understand specific visual requirements. Certain roles might be better suited to your capabilities.
In summary, while there are challenges, it's possible to secure a ground staff position if your visual impairments can be managed effectively and do not compromise safety or job performance. Consult with potential employers about the specific requirements and consider roles that align with your abilities.
Hey there,
With a GATE score of 26.00 in the 2024 exam, getting admission to COEP (College of Engineering Pune) for M.Tech in Power Electronics might be challenging as the cutoff scores for COEP are typically higher. However, cutoffs can vary each year based on several factors, including the number of applicants and their scores. It is recommended to check the previous years' cutoffs for COEP and apply through the GATE counseling process to see if you can secure a spot.
But you can get other colleges. If you want to get a list of all possible colleges in which you can get admission at your GATE score then,
I would recommend you to use GATE college predictor tool by Careers360 to get the list of possible colleges you can get with your score.
Here is the link to the tool:
https://engineering.careers360.com/gate-college-predictor?utm_source=qna&utm_medium=ini-gate_cp
Click on the above link, fill the required details and you will get the list of possible colleges at your rank.
I hope this answer helps you. If you have more queries then feel free to share your questions with us we will be happy to assist you.
Thank you and wishing you all the best for your bright future.