Message #167273

[[5025]]

OK, now we shall begin the next class period.  We will be discussing Kirchhoff's Laws (not to be mistaken with Kirchhoff's Laws of Heat Transfer) and Ohm's Law.

Because we have already discussed the units and properties of current, we shall now move on to voltage (electric potential difference) and resistance, which is NOT to be confused with impedance.

Chalkboard

Resistance is measured in Ohms.  The unit is the capital Greek letter, omega: "Ω".



Voltage is measured in Volts.  The unit is the capital letter, V: "V".

End Chalkboard

If you have not already learned about Potential Energy in physics, all the better for you.  There is a big difference in Electric Potential and Physical Potential.  

Chalkboard

The formula that relates Voltage, Resistance, and Current is Ohm's Law.





End Chalkboard

We will now work an example using Ohm's Law.

Chalkboard

Circuit:
 
  i
--->

-----  
      |   +
      |
      \
      /    Vr
      \
      /
      |
      |    -
-----

The resistance of the resistor is given to be 5 Ohms.  The current flowing through the circuit is given to be 10 Amps.  Calculate the Voltage drop over the resistor, Vr.

V=IR

V=(5 Ohms)*(10 Amps)

V=50 Volts

End Chalkboard

Are there any questions so far?