AP L5 Ohm_s Law and its explaination.pptx

science

1. Contents 1 1. Ohm’s Law 2. Relationship of Voltage, Current, Resistance 3. Calculating Voltage, Current, Resistance

2. Introduction In 1816 Georg Simon Ohm found that current, voltage, and resistance are related in a specific and predictable way. Ohm expressed this relationship with a formula that is known today as Ohm's Law Ohm's law describes mathematically how voltage, current, and resistance in a circuit are related. 2

3. 3 Ohm determined experimentally that if the voltage across a resistor is increased, the current through the resistor will also increase; and, likewise, if the voltage is decreased, the current will decrease .

4. 4 Ohm also determined that if the voltage is kept constant, less resistance results in more current, and, also, more resistance results in less current.

5. 5 Ohm's law states that current is directly proportional to voltage and inversely proportional to resistance .

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7. The Linear Relationship of Current and Voltage: In resistive circuits, current and voltage are linearly proportional. Linear means that if one of the quantities is increased or decreased by a certain percentage, the other will increase or decrease by the same percentage, assuming that the resistance is constant in value. For example, if the voltage across a resistor is tripled, the current will triple. 7

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9. 9 Let's take a constant value of resistance, for example, 10.0, and calculate the current for several values of voltage ranging from 10 V to 100 V in the circuit in Figure. The current values obtained are shown in Figure. The graph of the I values versus the V values is shown in Figure. Note that it is a straight line graph. This graph tells us that a change in voltage results in a linearly proportional change in current.

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11. 11 As you have seen, current varies inversely with resistance as expressed by Ohm's law, I = VR. When the resistance is reduced, the current goes up; when the resistance is increased, the current goes down. Let's take a constant value of voltage, for example, 10 V, and calculate the current for several values of resistance ranging from 10 n to 100 n in the circuit in Figure. The values obtained are shown in Figure. The graph of the I values versus the R values is shown in Figure. The Inverse Relationship of Current and Resistance

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13. 13 Calculating Current : Solution :

14. If the resistance is 47 ohm and the voltage is 50 volt, what is the current? If V= 5 V and R=1000 ohm, what is the current? If V= 50 V and R=1 K ohm, what is the current? If V= 50 V and R=10 K ohm, what is the current? 14 Related Problems :

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16. 16 If V= 25 V and R=1.8 M ohm, what is the current? 2. If R is doubled in the circuit, what is the new value of current?

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18. Calculating Voltage 18

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23. The End