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INTRODUCTION TO ELECTRICITY Circuit Fundamentals
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E LECTRICITY E LECTRICITY Electricity: Current electricity is the flow of charged particles along a conductor.
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C IRCUIT F UNDAMENTALS To operate, an electrical device requires electrical energy, which is provided by a steady flow of charged particles along a closed loop. This closed loop is called an electrical circuit. The circuit must form a closed loop so that the charged particles charges moving through the conductorcan return to the battery.
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C IRCUIT F UNDAMENTALS A circuit contains: a source of electrical energy, such as a battery a conductor, such as a wire a load that changes electrical energy into light, sound, heat, or motion
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C IRCUIT F UNDAMENTALS
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C URRENT A NALOGY Highway 401 in the Toronto area is the busiest highway in North America. If you were to stand beside the highway and count the cars as they passed, you would find that about 17 500 cars pass by every hour — that is about4.8 cars a second or over 420 000 cars a day!
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C URRENT The amount of charge transferred per unit time is referred to as current.
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C URRENT Current is represented by the symbol I, and is measured in amperes (A). Since current is the amount of charge that is transferred per unit time, the equation for current is: where I is the current in amperes (A), q is the amount of charge in coulombs (C), and t is the time in seconds (s).
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T YPES OF C URRENT A steady flow of current in one direction, known as direct current, or DC. Alternating current, or AC, changes direction periodically. That is, the charges in the wire move back and forth over the same spot and do not actually move from one terminal to another.
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T YPES OF C URRENT
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R ESISTANCE A NALOGY Highway 401 in the Toronto area is the busiest highway in North America. If you were to close one lane all 420 000 cars would have to use the same lane There is less space so car must slow down
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R ESISTANCE Resistance is the degree to which the flow of current is opposed in a circuit. A resistor is a device that resists or restricts the flow of current
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E LECTRIC P OTENTIAL Electrons repel each other. So when there is build up of charge the electrons will spread out. If the electrons are held in one space this gives the electrons potential energy. Much like a spring being squished
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E LECTRIC P OTENTIAL We define electrical potential as the electrical potential energy per unit charge. Electrical potential is represented by the symbol V, and its units are volts (V). It can be written mathematically as:
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E LECTRIC P OTENTIAL A NALOGY Object Drop Demo The higher the water the more POTENIAL ENERGY it has Therefore there is more energy per kg for the water on top than on bottom Therefore there is a Potential difference 5 J / Kg at the top 1 J / Kg at the bottom Therefore potential difference is 4 J / Kg
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P OTENTIAL D IFFERENCE As charges pass through a load in the circuit, they transfer energy to the load. This change in potential is referred to as the potential difference (V).
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P OTENTIAL D IFFERENCE Potential difference is also referred to as voltage. The potential difference is always measured between two points in the circuit
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P OTENTIAL D IFFERENCE A potential difference of 10.0 V is measured across a resistor in a circuit. If a charge of 20.0 C passes through the resistor, how much electrical energy is dissipated as heat?
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C IRCUIT B ASICS
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