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# Physics prezi for that ohm's law thingy lesson presentation or something like that.

The relationship between Voltage, Current and Resistance can be expressed as three mathematical equations, Ohm's Law.
by

## Chris Hogue

on 5 May 2011

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#### Transcript of Physics prezi for that ohm's law thingy lesson presentation or something like that.

Voltage
Voltage is the electrical
force that drives current
arround a circuit and is measured
in volts. V. Current
Current is the ammount of electrical
flow through a circuit. Currrent is
measured in amps, A and expressed
in ohms's law as I I R V Resistance.

resistance is the opposition to the flow of current and is measured in ohms Ohms Law states that

The current in a circuit is directly proportional to voltage and the resistance of the circuit. By knowing any two pieces of
information about a circuit it is possible to work
out the third using Ohm's Law Example; This circuit has an input voltage of 9V

The LED needs 2V to illuminate.
The current in the circuit is 10mA

To enable the LED to work the voltage
must be reduced to 2V. This is done with
the use of a resistor (R1)

To calculate the resistance value, use the formula:
R=V/I The Math May Get Tricky

Yes, you should panic! First we need to establish how much voltage
we need to lose.

Input=9V
LED=2V
9-2=7

Resistor R1 must suppress 7V We now have two bits of information about the circuit;

The current is 10 mA, the voltage R1 needs to suppress is 7V. Now we substitute these values into
the ohm's law equation.

R=V/I
R=7/0.01
R=700

The value of R1 is 700 Using Ohm's Law

Povided we know two bits of infomation
about a circuit we can rearrange ohm's
law to calculate the third.

R=V/I
I=V/R
V=IxR X Allways double check!

To check your calculations try working out Voltage or Current
now you know the value of R1.
Try changing the input voltage to:

6V
4.5V
3V

What happened to the value of R1? Ohm's Law The End
Lesson taught by Chris and Ross A lot!!! Insert applause now.
Full transcript