IB+MYP+Energy

**Energy, Work and Power**
__Describe characteristics of each energy and where it comes from.__ Please refer to ppt document on iLearn for details.
 * Types of Energy**
 * **G**ravitational Potential Energy ||
 * **L**ight Energy (Radiant) ||
 * **E**lectrical Energy ||
 * **E**lastic(Strain) Potential Energy ||
 * **N**uclear Energy ||
 * **S**ound Energy ||
 * **T**hermal Energy ||
 * **I**nternal Energy ||
 * **C**hemical Potential Energy ||
 * **K**inetic Energy ||


 * Sankey diagram** >> Transformations of Energy

**__Efficiency__**
For example, a street lamp uses 100 joules of electrical energy. 75 joules of this are wasted as thermal energy and only 25 joules are converted into light (the useful energy). ====**Efficiency** = 25 joules / 100 joules = [= 25 % ] ====
 * //Efficiency = Useful Energy / Total Energy In //**

**//__The principle of the conservation of energy__ says that//** **//'It is impossible to __ create __ or __ destroy __ energy.'//** **//'It can only be __ changed / transformed __ from one form to another.'//** **//ie. When a brick is dropped from a height, its P.E. decreases, but its KE increases.//**

Energy song iTube

=__**Energy, Work and Power**__=
 * < **What is Energy?** ||< **What is Work?** || **What is Power?** ||
 * < Energy is __ ability __ / __ capacity __ to do work.

The unit is the __ Joules __ [__ J __]. 1KJ is equal to __ 1,000 __J.

1-1. A flea of mass 0.4 mg leaves the ground, as it jumps, at about 1ms^-1. What is its KE? 1-2. How high does it jump? ||< Work is **the use** of **__ force __** to move an object some __ distance __. It is energy transferred by force.
 * __KE-PE Example__: Jumping flea**

The unit is the __ Joules __ [__ J __], Newton metre. To do work on an object some part of force that you exert must be in the **same** **direction** as the object's motion. || Power is the amount energy transformed per unit time. It is the rate at which work is done.

The unit is the __ Watt __ [__ W __], joules per second. || eg 1. A ball held above the Earth's surface has Gravitational Potential Energy. PE = mgh, where m=mass, g=gravity, h=height
 * < P.E is the energy a body has as a result of its position or the state of that body.

eg 2. Also, a stretched elastic band has PE due to its distortion.

N.B. PE is not the property of one body but of a system. ie. ball + Earth

K.E. is the energy an object has as a result of its motion. It depends upon its mass and velocity.

KE = 1/2(mv^2), where m=mass, v=velocity

KE doubles as mass doubles. KE increases as velocity increases. ||< ie. No work is done if there is no energy transfer.

Work done = Δ Energy

Work done is defined as scalar quantity. || The more powerful a machine is the faster it can do work.

eg. The more powerful a car is the faster it can climb a hill. || A 100g steel ball falls from a height of 1.8m onto a metal plate and rebounds to a height of 1.25m. Find 1. the PE of the ball before the fall 2. the KE as it hits the plate 3. its velocity on hitting the plate 4. its KE as it leaves the plate on the rebound 5. its velocity of rebound ||< Example 1: Lifting an object with force F, found from mg, through a distance, d will require, Fxd, energy. **Only if d is vertical motion.** If d is horizontal, there is **__no__** motion against the force. || Example: A body of mass 5kg falls from rest and has a KE of 1,000J just before touching the ground. Assuming there is no friction and using a value of 10ms^-2 for the acceleration due to gravity, calculate 1. the loss in PE during the fall, 2. the height from which the body has fallen 3. Name an important principle which applies in this situation. ||< Example 2: inclined plane
 * = **E = VIt** ||= **W = Force x distance = Fd** ||= **P** **=** **Work done / Time taken** **=** **W / t** ||
 * < Example 1: (g=10ms^-2)
 * If 1Joule of work is done in 1second, then the power will be P = 1/1 = 1 W ||
 * < Example 2:

W (Work) = Fd (F=mg, d=h) = mgh || ie. Alternative equations to find power used We know that the energy used by a component can be found from E= VIt then, P= E/t therefore, **P = VI** However, we know that V = IR therefore, **P = I** 2 **R** Also from I = V/R therefore, **P = V** 2 **/ R** || Check your Energy, Work and Power video on iTube

__**Work, Energy and Power from Physics classroom**__ __**Work, Energy and Power Review from Physics classroom**__

AC and DC
** Electricity consumption in your household ** V = W/Q, Q = It, P = W/t, W = VQ = VIt and W = Pt thus, P = VI Ex) 3V, 0.4A is written on the packet of torch bulbs. 1. Calculate the power conversion for the bulb in normal use. P = VI = 3V x 0.4A = 1.2 W 2. The life of the bulb is approximately 100 hours. How much energy will it have dissipated in its life time? Energy consumption: E = Pt = 1.2 W x 100 hours = 1.2 W x 360000 s = 432000 J


 * Calculate estimated electricity cost of your household for a month.**

Questions:

1. What are your daily, weekly and monthly electricity consumption?

2. Estimate your electricity cost.

3. What is the biggest electricity consuming device?


 * Items || Power of electronic device in watts || Number of device in your house || Daily time estimation using the device in hour || Daily Electricity Consumption in kWh || Weekly E.C. in kWh || Monthly E.C. in kWh || Electricity cost per hour in Shanghai || Monthly Electricity Cost in your household in RMB ||  ||
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4. What is your actual monthly electricity cost?

5. What are your strategies to reduce your electricity consumption?

__**Light my fire!**__ Matchlock: A gunlock in which powder is ignited by a match.
 * Flint:** A very hard, fine-grained quartz that sparks when struck with steel.

The chemical energy released from the burning of fuel in a power station is carried by means of the electric current to the lamp. When the electric current passes through the filament, the filament warms up. Its temperature rises so that it glows red or white hot. The energy is transferred from the filament as electromagnetic waves of visible light and infrared radiation which spread out into the surroundings, so warming up the environment.

You have shown that the energy radiated depends not only on the current but also on the potential difference. It will also depend on how long the current is flowing: Energy transferred by the electric current, //E = V x I x t = Pt//

The volt can be defined as the energy transferred per coulomb passing from a power supply to a component. This definition is frequently used when students are learning electrical concepts in the early stages**//.//**


 * Energy Worksheet[[file:Physics_Energy_Revision_Higher_teir.doc]]**

Link to [|Ms. Dunnett's Haiku class]

[|Energy teach and learn] from energy.gov