8/28/2023 0 Comments Define current voltage resistance![]() The current flowing through a component is measured by an ammeter. The voltage of the cell is always split amongst the components – none is left over. ![]() The voltmeter measures the difference in energy from before (2J) to after (0J). At the motor, the charge loses 2J of energy, so the lamp has a voltage of 2V.The voltmeter measures thedifference in energy from before (6J) to after (2J), At the lamp, the charge loses 4J of energy, so the lamp has a voltage of 4V.The voltmeter measures the difference in energy from before (0J) to after (6J) to work out the voltage. At the cell, the charge gets given 6J of energy, so the cell has a voltage of 6V (6J per coulomb of charge that passes).This diagram shows 1 coulomb of charge moving around a circuit. So the voltmeter measures voltage (potential difference) across two points.Ĭurrent, Resistance and Potential Difference The voltmeter therefore measures the energy before and after the component to see the difference. Remember, a voltage for a component or cell is the energy transferred per coulomb. For components, the voltage tells us the amount of energy taken away from the charges in the circuit. For cells or batteries, the voltage tells us the amount of energy given to the charges in the circuit. Voltage means different things for cells/batteries and components.It is measured between two points in a circuit. We can define voltage (potential difference) as the energy transferred per coulomb of charge that passes. Voltage is the energy transferred per coulomb of charge.For example, a buzzer uses energy to produce sound. Components – in contrast, components take energy away from charge as it passes.The energy given to the charges as they pass is measured in volts (V). Cells or batteries – The cells or batteries transfer energy to the charge as it passes in the circuit.In a circuit you can have cells / batteries and components: Please leave a comment below if you have any questions.Electricity - 2.2.3 Current, Resistance and Potential Difference (GCSE Physics AQA) Potential Difference Cells and BatteriesĪs we said above, cells or batteries are required to move charge around the circuit. May I recommend you print this note and check things off as you have master the topics. Know that it will take some time for the material to sink in. As the inductor is "turned off" it will act as a constant current source and do whatever is necessary to maintain the same current before and after the transition.Ĥ) Please search "transistor characteristic curves." Here you will find that a transistor appears to operate as an acceptable constant current source. Such a device would demand infinite current (again, not possible in this universe).ģ) Please search "inductor kickback." Here you will find than an inductor acts as a constant current source for a limited amount of time. Note that there is no such thing as a perfect constant voltage source. ![]() To make one you would need a device that could produce an infinite voltage (not possible).Ģ) Please search "Thevenin Norton Equivalent." Here you will find that a voltage source with series resistance can be modeled as a current source with parallel resistor. To my knowledge there are no perfect constant current sources. ![]() It will take on whatever voltage is necessary to do so including both positive and negative voltages. I'll give you a few examples to consider:ġ) The current source is a mathematical construct that maintains a constant current. The current source is a different animal. With more current and a fixed voltage there will be more power. As you stated as the resistance is decreased more current flows. Examples include a battery or wall outlet. In my opinion the voltage source is relatively straightforward. CAUTION - this is an answer from an electrical engineer.
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