1 / 9

Dynamic Electricity: Electric Energy &Power

Dynamic Electricity: Electric Energy &Power. Electric Power. The electric power of a machine is an indication of the amount of work it can do, that is, the amount of energy it can transform in a certain amount of time .

lucien
Download Presentation

Dynamic Electricity: Electric Energy &Power

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Dynamic Electricity: Electric Energy &Power

  2. Electric Power • The electric power of a machine is an indication of the amount of work it can do, that is, the amount of energy it can transform in a certain amount of time. • Therefore, the more powerful a machine, the faster it works. Also, the more work it can do in a set period of time, the more powerful it is.

  3. Power is a measure of the rate of transformation of electrical energy. The unit for electric power is the watt, W. A machine that has a power rating of 1 W provides 1 joule of work per second: 1 W = 1 J/ 1 s P = E / ∆t where P is electrical power measured in watts, W E is electrical energy in joules, J ∆t is the amount of time that has passed in seconds, s

  4. Relationship between Power and Energy It is possible to determine the quantity of energy consumed by an electrical device by multiplying its power by time: 1 W x 1s = 1 J/s x 1 s = 1 J P x t = E Energy can be measured in Joules, J, but it can also be measured in kilowatt hours (kWh). 1 kWh = 1000 W x 3600 s = 3 600 000 J

  5. Example : A 1000 W microwave is used for 6 minutes. How much energy (in Joules) will it consume? E = P x t = 1000 W x 6 minutes x 60 seconds/minute = 36 000 J The microwave will consume 36 000 J (or 36 kJ) of energy in 6 minutes.

  6. Power, Voltage, Current and Resistance Recall that 1V = 1 J/C; in other words if a resistor's voltage drop is 1 V, then 1 J of energy has been lost for every coulomb of charge that goes through that resistor. Also, 1 A = 1 C/s; in other words if a 1 A current goes through a light bulb, then it means that 1 C of charge is going by every second. Now let's multiply the units of V by those of I. (J/C) (C/s) = J/s. Those are the units for power! So that means: P = VI or substituting Ohm's Law P = I2R

  7. Example What is the power rating of a 10 Ω resistor that operates at 120 V. P = E x t = V x I = I2 x R I = V/R = 120 v/ 10 Ω = 12 A P = V x I = 120 V x 12 A = 1440 W The 10 Ω resistor has a power rating of 1440 W.

  8. Relating Energy to Power Since by definition E = P x t, where if P is power in watts( J/S = W) and time is measured in seconds, then E will be in joules (J). Substituting P = VI in to the above formula: E = V x I x t

  9. Example A heating coil has a resistance of 10 Ω. It is designed to operate at 120 V. If it is on for 200 hours, how much energy was consumed? E = V x I x t = 120 v x 12 A x 200 h x 60 minutes/hour x 60 seconds / minute = 1 036 800 000 J = 1 036 800 kJ The heating coil will consume 1 036 800 kJ in 200 hours.

More Related