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
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