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Current, voltage and resistance

Current, voltage and resistance. Revise the following: Circuit symbols Circuit diagrams Current and voltage in series circuits Current and voltage in parallel circuits. Circuit symbols. Current, voltage and resistance. Current = the rate of flow of electrons in a circuit

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Current, voltage and resistance

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  1. Current, voltage and resistance Revise the following: • Circuit symbols • Circuit diagrams • Current and voltage in series circuits • Current and voltage in parallel circuits

  2. Circuit symbols

  3. Current, voltage and resistance • Current = the rate of flow of electrons in a circuit • Voltage/potential difference = the difference in electrical potential energy between two points in a circuit. Potential difference is also called voltage • Resistance = a measure of how hard it is for electrons to move in an electrical circuit.

  4. A A Current in a series circuit • In a series circuit, the current flows through one continuous pathway so the current is the samein all parts of a series circuit. 1A 1A A 1A

  5. Voltage in a series circuit V V In a series circuit, the voltage supplied by the battery is shared by the components so the sum of the potential difference across the componentsequals the battery voltage. 6V V 3V 3V As more bulbs are added in series, eachbulb has less potential difference and so the bulbs become dimmer.

  6. Current in a parallel circuit A A In a parallel circuit, the current divides at the point where the circuit branches and then recombines to complete the circuit so the current is not the same in all parts of a parallel circuit. 2A 2A 1A A A 1A

  7. Voltage in parallel circuits V V 6V V • In a parallel circuit, the potential difference across each bulb is the same as the potential difference across the battery. 6V • This means that all the bulbs have the same brightness, and they are brighter than the same number of bulbs in a series circuit. 6V • This also means that the battery will run down faster in a parallel circuit.

  8. Georg Ohm (Ohm’s Law) • Resistance is a measure of how hard it is for electrons to move in an electrical circuit. • It was such an important discovery in electricity that the unit of resistance is called the ohm. • The formula used to calculate Resistance is called Ohm’s Law • This unit is represented by the symbol Ω. • In 1827 a German physics and maths teacher Georg Ohm discovered a connection between current, voltage and resistance

  9. voltage current V I voltage = current x resistance V = I x R resistance = R = What is the formula/equation for Ohm’s law? Ohm’s law is usually written as: This formula can also be written as: • Voltage is measured in volts (V). • Current is measured in amps (A). • Resistance is measured in ohms ().

  10. Current-voltage graphs A resistor at constant temperature Potential difference is directly proportional to current. As pd/voltage doubles, current doubles As pd/voltage triples, current triples Diode No current when pd/voltage is negative. When pd/voltage reaches a certain positive voltage, current increases and is directly proportional to pd Filament lamp A smooth curved line which levels off

  11. Resistance...

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