Voltage differences cause electric charges to move

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​How much charge moves through a wire per second is called electric current.

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Units: Amps (A)​

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​When you connect one end of a battery to the opposite end (+ to -), current will flow.

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How much current will flow is based on if there is anything in between...like a light bulb!

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​Things like lightbulbs have a resistance that limits current.

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In general we call them resistors.

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Units for resistance is Ohms (Ω)

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The relationship between voltage, current, and resistance is:

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V = I*R​

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Ohm's Law​

​Ohm's Law tells us that if we want a lot of current, we need either a lot of voltage, little resistance, or some combination of both.

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A 9V battery is connected across a lightbulb with 10Ω of resistance.

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What is the current through the light bulb?

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V = I*R

I = V/R

I = 9/10 = 0.9 A​

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0.9A is going through the lightbulb​

1A of current is going through a light bulb with 20Ω or resistance.

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What is the voltage across the light bulb?​

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​V = I*R

V = 1*20

V = 20 V

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20V are across the light​bulb

12V are put across a lightbulb, and a current of 2A flows through the light.

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What is the resistance of the light bulb?

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V = I*R

R = V/I

R = 12/2 = 6​Ω

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​The lightbulb has a resistance of 6​Ω

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Summary