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Transcript
Voltage, V • Voltage tells us how hard a positive charge is pushed between two different points. • Something, such as a battery, is needed to create a voltage. Current, I • Current tells us the amount of charge flowing through something (similar to gallons per minute). • Current must have a path through which to flow. • Wires provide a path for current flow (and offer no no resistance to the flow). What Are These? + V – Battery Wires Switch Light Bulb New Symbols V + V – Battery Switch Old Circuit Drawing A Push to Close Y New Circuit Drawing V How Much Current Flows? V Switch is open. Zero. This is an “open circuit.” How Much Current Flows? V Switch is closed. TOO MUCH!!! This is a “short circuit.” How Much Current Flows? V Light bulb has resistance to flow of charge. Amount of resistance is some number R. Resistor Symbol R Electrically: Light Bulb = Resistor V V I Current, I = V / R R LED: A Different Kind of Light Bulb • LED = Light Emitting Diode • Current can only flow in one direction (in direction of arrow). • Light only emitted when current flows. • A lot of current may flow if a large large voltage is across an LED. Dangerous LED Circuit V When switch is closed, too much current may flow! Almost behaves as a short circuit. Need to modify circuit to limit current… Good LED Circuit V When switch is open, light is off. When switch is closed, light is on. Resistor limits current flow. R Good LED Circuit 5V0 V R GND