# Principles of Physics. Ideal Physics World  No energy loss  Resistance only in resistors Real World  Resistance in wires  Resistance causes heat 

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Principles of Physics

Ideal Physics World  No energy loss  Resistance only in resistors Real World  Resistance in wires  Resistance causes heat  System loses energy

 Georg Ohm experimented with various materials  He found out that V is proportional to I in ideal materials (I) VOLTAGE (V)

I = V/R → R = V/I → V = IRV = Voltage (V) I = Current (A) R = Resistance (ohm = Ω )

 Light bulbs are resistors  They give off light and heat  Brightness increases as current increases  Since energy is lost as light and heat more voltage is required to have the same current  As current increases, resistance increases because the light bulb heats up Voltage Current

 A voltage exists across every device (voltage supply, resistors, light bulbs, etc.)  As an electron goes through a resistor or device it loses energy because it does work to get through  How much energy lost per Coulomb (V) depends on the resistance

 Voltmeters are used to measure voltage across devices  Ammeters measure current through devices

A V  Ammeters must be connected in the same path as the device  Voltmeters must be connected across the device

 On all voltmeters and ammeters there are three ports:  Black is always connected to the circuit  Only one red port is connected to the circuit  Each port correlates to a different scale (number below the port is the highest number on the matching scale)

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