Ohm’s LawOhm’s LawThe most important fundamental law in electronics is Ohm’s law,

which relates voltage, current, and resistance.

Georg Simon Ohm (1787-1854) studied the relationship between voltage, current, and resistance

and formulated the equation that bears his name.

Summary

Voltage is

Review of V, I, and R

the amount of energy per charge available tomove electrons from one point to another in a circuit.

Current is the rate of charge flow and is measured in amperes.

Resistance is the opposition to current and is measured in ohms.

SI unit for voltage is volts (v)SI unit for current is amps (A)

SI unit for resistance is ohms (Ω)

VI

R

What is the current in from a 12 V source if the resistance is 10 ? 1.2 A

If you need to solve for current, Ohm’s law is:

If you need to solve for voltage, Ohm’s law is:

V IRWhat is the voltage across a 680 resistor if the current is 0.25 A? 170 V

If you need to solve for resistance, Ohm’s law is:

What is the resistance of the bulb?

115 V

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PracticePractice What value of resistor would be used to What value of resistor would be used to

permit a current of 0.2 A to flow using a 6V permit a current of 0.2 A to flow using a 6V supply? supply?

Calculate the voltage across a 300 ohm Calculate the voltage across a 300 ohm resistor when a current of 0.004 A flows resistor when a current of 0.004 A flows through it. through it.

A resistor allows a current of 0.6 A to flow A resistor allows a current of 0.6 A to flow when connected to a 9.6 volt supply.when connected to a 9.6 volt supply.What current would flow if the same resistor What current would flow if the same resistor was connected to a 12.8 V supply? was connected to a 12.8 V supply? R=V/I

I=V/R

V=IR

R=V/I R=6/0.2 R=30Ω

V=(0.004)(300)

V=1.2V

R=9.6/0.6 R=16ΩI=12.8/16 I=0.8 A