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Published byJason Pierce Modified over 9 years ago
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Electric Current Charges on the move!
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What makes a charge move? Electric current moves due to potential difference Electric potential difference is measured as voltage – Potential difference is measured in volts (V) The flow of charges due to potential difference is current electricity
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What makes charges move? Charges must have a pathway to move Pathway is called a circuit Circuit must have certain parts: – Source (area of high potential) – Path (usually wire) – Load (something that does work using the moving charges) – Sink (area of low potential)
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What makes charges move? Source of potential difference may be direct current Batteries produce direct current due to a chemical reaction Voltage produced by chemical reaction can travel through wire to load Two kinds of battery: – Dry cell: two elements and chemical paste – Wet cell: two metals and liquid electrolyte
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What makes charges move? Source of potential difference may be generator Generator moves wire in magnetic field to create alternating current (AC)
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How many charges move? Amount of moving charges is called current Current measured in Amperes (amps) (A) Current is number of charges moving past in one second (Coulombs/sec)
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Why do charges lose potential? Resistance: similar to friction, resistance slows down charges Resistance measured in Ohms ( Ω) Size of wire affects resistance –Longer wire has more resistance –Thicker wire has less resistance Load in the circuit is a resistance
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Ohm’s Law Relates current, potential difference, and resistance Current = voltage / resistance I = V/R We can use our circle with this!
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Ohm’s Law Example Calculate the voltage difference across a 25 Ω resistor if a 0.3 A current is flowing through it? Step 1: What do we know? –Know R = 25 ΩI = 0.3 AV = ? Step 2: What equation will we use? V = I R
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Ohm’s Law Example Continued Step 3: Plug in info! – V = (0.3 A)(25 Ω) Step 4: Do the math – V = 7.5 V Step 5: Check for units!
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