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Transcript
Resistance and Ohm’s Law SPH4C Resistance is the property of substances that impedes the free flow of electrons. Resistance Resistance is the property of substances that impedes the free flow of electrons. It is measured in units of Ohms (W). Resistance Loads such as lights and heating elements have a resistance: they impede the flow of electrons and convert the energy of electrons into another form of energy such as light or heat. Loads and Resistance A resistor is a load placed in a circuit simply to impede the flow of electrons and thus control the current to the rest of the circuit. Resistors The resistance of a resistor is typically indicated by colour-coded bands: Resistors and Resistance The resistance of a resistor is typically indicated by colour-coded bands: Resistors and Resistance The resistance of a resistor is typically indicated by colour-coded bands: Resistors and Resistance The resistance of a resistor is typically indicated by colour-coded bands: Resistors and Resistance The current that flows through a resistor will be equal to: V I R Resistance and Current The current that flows through a resistor will be equal to: V I R This is called Ohm’s Law and often written: V IR Resistance and Current If a 50-W resistor is connected to a 1.5 V battery, what is the current through the resistor? Example If a 50-W resistor is connected to a 1.5 V battery, what is the current through the resistor? R 50 W V 1. 5 V I ? Example If a 50-W resistor is connected to a 1.5 V battery, what is the current through the resistor? R 50 W V 1. 5 V I ? Example V I R 1.5V I 0.03 A 50 W or 30 mA If a 50-W resistor is connected to a 1.5 V battery, what is the current through the resistor? R 50 W V 1. 5 V I ? Example V I R 1.5V I 0.03 A 50 W or 30 mA If a 50-W resistor is connected to a 1.5 V battery, what is the current through the resistor? R 50 W V 1. 5 V I ? Example V I R 1.5V I 0.03 A 50 W or 30 mA