# Ohm's Law

## Greater voltage results in more current and greater resistance results in less current. Current (Amps) = Voltage / Resistance

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How Can You Resist?

### How Can You Resist?

Credit: Tylercat5
Source: http://commons.wikimedia.org/wiki/File:MV_Lamp_175_W.JPG

Do you see the small blue and silver cylinder near the bottom of this mercury-vapor light bulb? It’s an electrical device called a resistor.

#### The Back Story

• A resistor is a device used to regulate the amount of electric current in a circuit. Resistors are used in light bulbs and appliances to limit the amount of current that reaches them. They work by resisting the flow of current through the circuit.
• Credit: US CPSC
Source: http://www.flickr.com/photos/uscpsc/8723105569/

Electric heaters use resistance to generate heat instead of light [Figure2]

• Resistors come in different sizes. Which size does a device need? You can use Ohm’s law to find out.
• Ohm’s law states the relationship among voltage, current, and resistance in a simple electric circuit. For a better understanding of these relationships, experiment with this applet: http://www.physics.uoguelph.ca/phyjlh/Fendt/phe/ohmslaw.htm

#### Can You Apply It?

1. State Ohm’s law and represent it with a formula.
2. What SI units are used for the variables in the formula for resistance in question 1?
3. How many ohms of resistance does a resistor need to provide for a 12-volt circuit to carry 6 amps of current?
4. How much current does a 120-volt circuit carry if it contains a resistor that provides 10 ohms of resistance?
5. What do you think might happen to an appliance in a circuit if the wrong resistor is used so the appliance gets too much current?

### Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes

1. [1]^ Credit: Tylercat5; Source: http://commons.wikimedia.org/wiki/File:MV_Lamp_175_W.JPG; License: CC BY-NC 3.0
2. [2]^ Credit: US CPSC; Source: http://www.flickr.com/photos/uscpsc/8723105569/; License: CC BY-NC 3.0

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