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ELECTRICAL CIRCUITS
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What is this a picture of?
- +
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What is electric current?
Electric Current (I) - a flow of electrons from the (+) terminal to the (-) terminal of a cell/battery through wires and components - +
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Open and Closed Circuits
Open circuit = switch is open = no current is flowing = bulb does not light Closed circuit = switch is closed = current is flowing = bulb lights up
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Circuit Diagram & Symbols
Cell/Battery Resistor Light Bulb Light Bulb Resistor Wires Switch
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Types of Circuits Series Circuits – current takes only one path and is the same at each point. (One Wire connects ALL)
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Series Circuits If one bulb blows out, it breaks the circuit and all the bulbs go out If you add more cells/batteries to a series circuit, the bulbs burn brighter
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Types of Circuits Parallel Circuits – current takes more than one path and is NOT the same at each point. (Multiple Wires)
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Parallel Circuits If one bulb blows out, there is still another complete circuit for the other bulb to stay lit
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Draw these circuits in your Notebook
Draw these circuits in your Notebook. Label each one as either Series or Parallel. A – Parallel B – Series
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As a Quick Write in your notebook
Compare and contrast conductors and insulators, give examples as well. Discuss with your elbow partner.
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Conductor or Insulator?
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Brighter or Dimmer? Dimmer
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Series or Parallel? Series
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Brighter or Dimmer? Brighter
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Series or Parallel? Parallel
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Series or Parallel? Series
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Series or Parallel? Parallel
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Ohm’s Law
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Ohm’s Law
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The Resistance is halved!
What Happens? What happens to the Resistance when the Current is doubled and the Voltage stays the same? The Resistance is halved!
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The Voltage is Tripled too!
What Happens? What will happen to the Voltage when the Resistance is tripled and the Current remains constant? The Voltage is Tripled too!
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What Happens? What happens to the Current when the Resistance is reduced by 1/3 and the Voltage stays the same? The Current is Tripled!
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Measuring Current Current is measured in units of amperes or amps (A)
In a series circuit, current is the same at all the points In a parallel circuit, current is shared between all the points
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What is the current? SERIES CIRCUIT PARALLEL CIRCUIT 3A 3A 4A 1A 4A 1A
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Measuring Voltage Voltage – the electrical push that a cell/battery gives to the current Voltage is also known as Potential Difference Voltage is measured in units of volts (V)
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Measuring Voltage 3V 1.5V 3V In a series circuit, voltage is shared between all the points In a parallel circuit, voltage is the same at all the points
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What is the current and voltage?
Series Same Shared Parallel
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What is the current and voltage?
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In a series circuit, add up all resistance to get total.
Measuring Resistance Resistance – slows down current, adding components to a circuit increases resistance Resistance is measured in units of ohms (Ω) More resistance = Less current = Less light In a series circuit, add up all resistance to get total.
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Electrical Power
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How much voltage gives 5 amps of current through a 3 Ω light bulb?
I = V/R V = (5A) (3Ω) V = 15V
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How much current flows in a circuit with a 1
How much current flows in a circuit with a 1.5 volt battery and three 1 ohm resistances (bulbs) in series? I = V/R I = (1.5V) / (3Ω) I = .5A
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What is the voltage drop across each resistor in the circuit?
In a series circuit, voltage is shared between all the points 9V/3 = 3V
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P = IV I = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A) (1.5V) = 1.5 W
A light bulb with a resistance of 1.5Ω is connected to a 1.5V battery in the circuit. Calculate the power used by the light bulb? P = IV I = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A) (1.5V) = 1.5 W P = 1.5 W
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