Ohm's Law states that the current through a conductor is directly proportional to the voltage applied, provided the resistance remains constant. Georg Simon Ohm discovered this relationship in the 1800s and developed a mathematical formula relating voltage (V), current (I), and resistance (R) such that V=I×R. Various devices can measure these electrical properties, and changing the temperature of a resistor alters its resistance and causes Ohm's Law to break down.

1. Ohm’s Law

2. Ohm’s Law
 Georg Simon Ohm did a lot of work with
electricity in the 1800’s He found links between
voltage, current & resistance. He was able to
form a law (Ohm’s law) regarding resistance.
 If the resistance of a conductor stays constant,
then the current is directly proportional to the
voltage applied.

3. Ohm’s Law
 Devices that measure electricity:
 Voltmeters - measure voltage (in volts V)
 Milivoltmeters – tiny amounts of voltage (in mV)
 Ammeters measure - current (in amps A)
 Galvanometers measure - tiny amounts of current ( in
mA)
 Resistometers or Ohmeters meausure - resistance (in
ohms Ω)
 Multimeters – measure voltage, amps, and resistance

4. Ohm’s Law
 How can we graph the
relationship between current and
voltage?
 Draw the Graph

5. Ohm’s Law
 Ohm’s law does not work if there is a change in
temperature. When the temperature pf a resistor changes,
then its resistance changes,
 Resistance is lowest when a conductor is cool. As the
temperature increases the resistance increases.

6. Ohm’s Law
V = I x R
V = Voltage
I = Current
R = Resistance

7. Ohm’s Law

8. Ohm’s Law

9. Ohm’s Law
 Let’s try some!
1. A 30 V battery creates a current through a 15 Ω resistor.
How much current is created?
V = I x R
I =
𝑽
𝑹
I =
𝟑𝟎
𝟏𝟓
I =2

10. Ohm’s Law
 Let’s try some!
2. A motor has an internal resistance of 40 Ω. The motor is in a
circuit with a current of 4.0 A. What is the voltage?
V = I x R
V = 4.0 x 40
V = 160 V

11. Ohm’s Law