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8.1 Electric Potential Energy and Voltage Name: Date: Block: (Reference: BC Science 9 pp. 270 – 279) Storm clouds and batteries both separate _____________ and __________________ charges. battery: ____________________________________________ ____________________________________________________ ____________________________________________________ Technically, a battery consists of more than one electrochemical cell. o electrochemical cell: a device that converts _______________ energy into __________________ energy stored in _______________ (electrons). In a battery, chemical energy ____________________ the positive and negative charges on to ____________________. o terminals: _____________________________________ _____________________________________________ negative terminal: ___________ electrons positive terminal: __________ electrons ELECTRIC POTENTIAL ENERGY Energy is the ability to do work. o kinetic energy: _________________________________ _____________________________________________ o potential energy: ________________________________ _____________________________________________ The electrical energy stored in a battery is called ________________ ____________________ ______________ When a battery is connected to a device, the electrons flow from the _________________ terminal of the battery through a device and return to the ________________ terminal of the battery. o In the device, electric energy is converted into other forms of energy, such as _______, _________, or ________ energy. ELECTRIC POTENTIAL DIFFERENCE potential difference:________________________________ _________________________________________________ o unit= ________ (___) o named after Alessandro Volta who invented the first battery (1799). o Measured by a ______________________ Voltage is __________________ to the distance that the charges have been separated. o Ex. 1.5 V on a battery means a potential difference of 1.5 V. COMPARING POTENTIAL ENERGY AND POTENTIAL DIFFERENCE The amount of energy stored in a battery (potential energy) depends on two things: 1. ___________________________________ (________________) How far the electrons have been separated Unit: ____________ The _______________ of the battery amount of energy the electrons carry Ex. 1.5 V 2. _________________________________________ _____________________________________ (_____________). How many electrons have been separated Unit: ____________________ The _________ of the battery The number of electrons Ex. AA battery AAA, AA, C, and D batteries are all 1.5 V but are different sizes. D batteries are the largest, so have the most _______________ that can be separated = greatest potential energy. PRODUCING VOLTAGE The amount of voltage a battery produces depends on two parts: 1. electrolyte: ________________________________________ 2. electrodes: ________________________________________ usually made of _______ ______________ __________ (ex. zinc and copper), but can be a metal and another material. Batteries are classified into two groups: 1. Dry Cells electrolyte is a __________ ______________ o usually an alkaline material used in devices like flashlights, watches and portable electronics. 2. Wet Cells electrolyte is a _____________ o ex. dilute sulphuric acid used in cars, motorcycles, etc. **Both produce voltage in a similar way. How a battery works When a zinc and copper electrode are placed in an acidic electrolyte, through chemical reaction the electrolyte: o pulls atoms off the zinc electrode, leaving behind electrons on the electrode, causing it to become __________________ charged. o pulls electrons off the copper electrode, causing it to become _________________ charged. The resulting opposite charge on each electrode creates a ________________ _________________ (voltage) between the two electrodes. FIVE SOURCES OF ELECTRICAL ENERGY (Refer to Table 8.1 p. 274) Electrical Energy Sources 1. Definition Rubbing two materials together can separate charge. 2. Types of crystals (ex. quartz), that when squeezed separate charge on either side of the crystal. When light hits some semi- conducting materials (ex. silicon), electrons break off the surface of the material. Device used to transform heat energy into electrical energy. Is a loop of two wires of different metals joined at both ends. When heated or cooled, charge is separated and voltage created. 3. 4. 5. A wire moves close to a magnet or vice versa, a voltage is created across the wire. In BC, use hydroelectric energy as energy source to move the wire or magnet. SUMMARY: Example