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chp35ECircuits - the other branches unchanged 3 Voltage...

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Electrical Circuits An electrical circuit is a pathway through which electrons can flow. We’ll use hydraulic (water flow) analogs to illustrate circuits: player water electrical power source pump battery potential difference pressure drop voltage flow water current resistance turbine resistor (ex: light bulb, any assume zero resistance: in pipes in wires control valve switch 1
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Series and Parallel Circuits Series Circuit 1. There is only one pathway for current to flow. (Breaking the circuit anywhere stops all current.) 2. The current is the same everywhere. (Charge cannot build up due to electron repulsion.) 3. Resistances in series add up to higher resistance. Parallel Circuit 1. separate pathways (called branches) for cur- rent to travel through different devices. 2. current divides to flow through separate branches: (a) more current through lower resistance paths; less current through higher resistance paths (b) total current equals sum of currents entering or leaving the separate branches. (c) breaking one branch, leaves the currents in
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Unformatted text preview: the other branches unchanged. 3. Voltage drops across branches in parallel are the same . 4. Overall resistance decreases with the number of branches. 2 Parallel Circuits and Overloading Our electrical lines supply and maintain 120V. When more and more appliances (such as lamps and refrigerators) are hooked in parallel to an outlet (by a power strip): • The same 120 volts is across each appliance. • The Equivalent Resistance: R eq gets lower with the addition of more appliances. • The total current drawn increases: I T = V T R eq • The power drawn increases: P = V T I T = V 2 T /R eq If the current drawn is too high, we say the line is overloaded ; the results can be overheating, fires, damage to appliances. A Fuse : device that melts at a current lower than that which overload the line being pro-tected. (ex: Use an 8 amp fuse to protect against a damaging 10 amps.) The fuse must be hooked in series to protect the line. Why? 3...
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