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Power and Energy notes What do the atoms in a wire look like? What particles move in an electric circuit? What do we call the total amount of charge that passes a point each second in an electric circuit? What is the current in a circuit where 1 coulomb of charges pass a point each second? ___________ are the things that move in an electric circuit Current The amount of ________ (number of electrons) that pass a point in a given ________ is called _________ (symbol is I). Instead of individual electrons passing a point we talk about a group of electrons, 6.25 x 1018 or _________ of charge passing a point in a wire. If one _________ of charge passes a point in one _________ then you have 1 C/s of current …AKA… one _________ (1 A) I = q/t Which is constant for an electron: the charge or the energy it carries? The _________ of an electron never changes but the _________ they carry can change A) e- B) e- C) e- eee- Which of the pairs of electrons has the most charge? ________, the charges on the electrons are ___________. Which of the pairs of electrons has the most stored energy? The electrons that are the _________ __________, ___. What is the amount of energy per coulomb of charges called? Voltage The amount of _______ per _____________ of charges is called ______________. V= E/q Energy per charge would be measured in Joules/Coulomb … J/C… AKA… ________ (__). What is the voltage of a standard AA battery? A standard AAA battery? AAA, AA, C and D batteries are all _____ _______. 9V batteries are made from 6-1.5 volt batteries linked together in series. Notes on power Electrical devices need a certain amount of _________ each ___________ to operate. What is the amount of energy needed per second called? What are the units? The amount of _______ needed each _________ to operate is called ________ and is measured in _______. What is a Watt equal to? One Watt (W) is equal to One ________ of ________ per _________. (J/s) What is the equation to find power? P=IV P I EXAMPLE 1 - A circuit consists of a 12 volt battery creating a current of 3.0 amps. Determine the power supplied by the battery. EXAMPLE 2 – A 45 W circuit has 27 J of energy for every 3 C of charge. Determine the amount of charge that passes a point in the circuit every 5 seconds. V Notes on energy How can power be used to find total energy? ___________ indicates how much ________ is used in a given ______, to find the total energy used to operate a device we need to multiply ________ by the ________ of operation. E=Pt E P If power is in Watts and time in seconds, what is the unit for energy used? t If power is in Watts (J/s) and time is in seconds, when we multiply to find energy used the unit will be _______. This can lead to very large numbers for devices that are used for long periods of time or require large power. How much energy in Joules is used by a 1000 W water heater on for one hour? If power is in kW and time in hours, what is the unit for energy used? How much energy in kWh is used by the 1000 W water heater on for one hour? Another way to find energy used, as the power company does and as we will in this class on the HFE project, is in ______. For this, the ________ is changed from W to kW by dividing by _____. The power in kW is then multiplied by time in hours. This leads to smaller answers for energy that can be better understood.