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16.3 Resistance and Ohm’s Law

16.3 Resistance and Ohm’s Law. Ohm’s Law Entrance Slip. A toaster has a resistance of 12 ohms and is plugged into a 120-volt outlet. How much current does it draw?. Electrical Resistance. Resistance: how strongly a wire or other object resists current flowing through it.

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16.3 Resistance and Ohm’s Law

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  1. 16.3 Resistance and Ohm’s Law

  2. Ohm’s Law Entrance Slip A toaster has a resistance of 12 ohms and is plugged into a 120-volt outlet. How much current does it draw?

  3. Electrical Resistance Resistance: how strongly a wire or other object resists current flowing through it low resistance = large current high resistance = little current

  4. Electrical Resistance Every electrical device is designed with a resistor that causes the right amount of current to flow when the device is connected to voltage. A light bulb’s resistance increases when there is more current because the bulb gets hotter when more current passes through it.

  5. Measuring Resistance Resistors are used to control the current in circuits. Resistance is measured in ohms (Ω)

  6. Measuring Resistance Two types of resistors: 1. Fixed resistor: resistance cannot be changed 2. Variable resistor (potentiometer): resistance can be adjusted

  7. Conductors and Insulators • Conductor: a material with low electrical resistance • examples: metals Insulator: a material with high electrical resistance - examples: rubber, plastic

  8. Ohm’s Law The total amount of resistance in a circuit determines the amount of current in the circuit for a given voltage.

  9. Ohm’s Law

  10. Ohm’s Law Example • A battery supplies 3 V to a circuit and a light bulb has a resistance of 2 ohms. What is the current in amperes?

  11. Ohm’s Law Example • A current has two 9-V batteries that supply energy to a light bulb with a resistance of 6 ohms. How much current runs through the circuit?

  12. Ohm’s Law Example • A 1.5-V battery is used in a circuit with a light bulb. If 6 amperes of current runs through the circuit, what is the resistance of the light bulb?

  13. Ohm’s Law Example • Two 9-V batteries supply energy for two light bulbs. If 3 amperes of current runs through the system, how much resistance does each light bulb have?

  14. Entrance Slip Revisited… How’d you do? Look over your entrance slip for today and see if you change your answer. Take two minutes… A toaster has a resistance of 12 ohms and is plugged into a 120-volt outlet. How much current does it draw?

  15. Extra Example • A 3-V battery supplies energy to a circuit with a light bulb that has 2 ohms of resistance. What is the current?

  16. Extra Example 2 • You want a current of 10 amperes to run through a circuit. The light bulb has 6 ohms of resistance. How much voltage must be supplied to the circuit?

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