Today we are going to look at:

Current: Measured in “Amperes” or “Amps” (A)

“The rate of flow of electrons through a circuit”

Voltage: Measured in “Volts” (V)“Used to drive the electrons through the

components”

Resistance: Measured in “Ohm’s” ( )“A measure of how much voltage is

required to let a current flow”

Georg Simon Ohm (1787-1854)

Ohm formulated the relationship between voltage, current & resistance as follows.“The current in a circuit is directly proportional to the applied voltage and inversely proportional to the resistance of the circuit”

“Voltage (V) is equal to the current (I) multiplied by the resistance (R)

If we use a triangle to help us, then we can arrange the formula to make it easier to use.

V

I R

This gives us the formula’s

V = I x R VI = R

VR = I

Example 1: Voltage

Q: The resistance of a circuit is 12 and the current is 2A. What is the voltage?

Step 1: Draw Triangle

V

I R

Step 2: Select correct equation

V = I x R

Step 3: Plug in the numbers

V = ?I = 2A & R = 12

Step 4: Calculate

V = 2 x 12

Step 5: Solution

V = 24V

Don’t Forget the units!

Now you try one!Q: The resistance of a circuit is 15 and the current is 3A. What is the voltage?

Example 2: Current

Q: The voltage supply is 25V and the resistance is 5 . What is the current

Step 1: Draw Triangle

V

I R

Step 2: Select correct equation

VI = R

Step 3: Plug in the numbers

V = 25V I = ? R = 5

Step 4: Calculate

I = 25 5

Step 5: Solution

I = 5A

Don’t Forget the units!

Now you try one!Q: The voltage supply is 40V and the resistance is 10. What is the current?

Example 3: Resistance

Q: The voltage supply is 300V and the current is 2A. What is the resistance?

Step 1: Draw Triangle

V

I R

Step 2: Select correct equation

VR = I

Step 3: Plug in the numbers

V = 300V I = 2AR = ?

Step 4: Calculate

R = 300 2

Step 5: Solution

R = 150

Don’t Forget the units!

Now you try one!

Q: The voltage supply is 500V and the current is 50A. What is the resistance?