Resistance 12/14/2007

Resistance 12/14/2007
Georg Simon Ohm
1789-1854

Resistance
Resistance is anything that will
RESIST a current. It is measured in Ohms, a unit named after me.
12/14/2007
Georg Simon Ohm
1789-1854

Resistance
Resistance is anything that will
RESIST a current. It is measured in Ohms, a unit named after me.
12/14/2007
The resistance of a component can be calculated using Ohm’s Law:
Georg Simon Ohm
1789-1854

Resistance
Resistance is anything that will
RESIST a current. It is measured in Ohms, a unit named after me.
12/14/2007
The resistance of a component can be calculated using Ohm’s Law:
Resistance = Voltage (in V)
(in
Ω
) Current (in A)
Georg Simon Ohm
1789-1854

Resistance
Resistance is anything that will
RESIST a current. It is measured in Ohms, a unit named after me.
12/14/2007
The resistance of a component can be calculated using Ohm’s Law:
Resistance = Voltage (in V)
(in
Ω
) Current (in A)
I
Georg Simon Ohm
1789-1854
V
R

An example question: 12/14/2007
Ammeter reads 2A
A
V
Voltmeter reads 10V
1) What is the resistance of this bulb?
2) Assuming all the bulbs are the same what is the total resistance in this circuit?

12V
More examples…
3A
6V
12/14/2007
4V
2A
1A
2V
3A
What is the resistance of these bulbs?

I
Current-voltage graphs 12/14/2007
I
V
I
V
V

I
Current-voltage graphs 12/14/2007
I
V
I
V
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
I
V
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
I
V
1. Resistor
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
I
V
1. Resistor
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
2. Bulb
I
V
1. Resistor
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
2. Bulb
I
V
1. Resistor
V
Explain the shape of each graph

I
Current-voltage graphs 12/14/2007
I
V
2. Bulb
I
V
1. Resistor
V
3. Diode
Explain the shape of each graph

Three simple components: 12/14/2007

Three simple components: 12/14/2007
1) Diode – only lets current flow in one direction

Three simple components: 12/14/2007
1) Diode – only lets current flow in one direction
2) Light dependant resistor – resistance DECREASES when light intensity INCREASES

Three simple components: 12/14/2007
1) Diode – only lets current flow in one direction
2) Light dependant resistor – resistance DECREASES when light intensity INCREASES
3) Thermistor – resistance DECREASES when temperature
INCREASES