voltage, v
DESCRIPTION
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). - PowerPoint PPT PresentationTRANSCRIPT
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 Battery
Switch
V
Push toClose
A
Y
Old Circuit Drawing
New Circuit DrawingV
How Much Current Flows?V
Switch is open.Zero.This is an “open circuit.”
How Much Current Flows?
Switch isclosed.
TOO MUCH!!!This is a “short circuit.”
V
V
How Much Current Flows?
Light bulb has resistanceto flow of charge.Amount of resistance issome number R.
Resistor Symbol
R
V
RI
VElectrically: Light Bulb = Resistor
Current, I = V / 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.
V
Dangerous LED Circuit
When switch is closed, too muchcurrent may flow!
Almost behaves as a short circuit.
Need to modify circuit to limitcurrent…
Good LED CircuitV
R
When switch is open, light is off.
When switch is closed, light is on.
Resistor limits current flow.
Good LED CircuitV
R
5V0
GND