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27 Cards in this Set
- Front
- Back
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What is current?
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The rate of flow of charge around a circuit.
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What is current measured in?
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Amperes (A)
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What does current need to flow?
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Voltage!
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What is Voltage?
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The driving force that pushes current around. like electrical pressure.
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What units is voltage?
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V
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What is resistance?
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Anything that slows flow down. If you add more components to the circuit there will be more resistance.
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What units for resistance?
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Ohm see page 21
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What is the balance between voltage and resistance?
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Voltage tries to push current around circuit. Resistance opposes the flow of current. The relative size of voltage and resistance affect how big current will be.
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What happens if you increase voltage?
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More current flows
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What happens if you increase resistance?
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Less current flows OR more voltage needed to keep same current!!
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What is an Ammeter?
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Measures the current in amps flowing through a component .
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Should an ammeter be in series or parallel?
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In series. We want to measure the current after it has passes through the component
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What is a voltmeter?
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Measures voltage ACROSS a component
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Should voltmeter be series or parallel?
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Parallel. Must be placed around the component under test so as not to add any resistance and not affect current.
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Draw the standard test circuit
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Here I am!
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Should an ammeter be connected in parallel or series
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series as measures amount of electrical flow in circuit. very low resistance so can be in series
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What is the standard circuit used for?
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Testing components and getting V-I graphs
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What must be in series
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The component under test. the ammeter and the variable resistor. They can be put in any order in circuit!!
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If you add components with resistance does the current reduce after each component?
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NO!! The overall current across all components is reduced the same
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What happens as you vary a variable resistor?
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It alters the current flowing through the circuit. This allows you to take several pairs of readings from the ammeter and voltmeter. you can then plot these on V-I graph
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What type of current is mains supply and battery
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AC for mains, DC for current
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What voltage is UK mains supply
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230v
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What does AC mean
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alternating current. means it is changing direction constantly
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What's so special about AC?
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Its current can be increased or decreased by a transformer. so in power lines the lower the current, the less energy is wasted as heat
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Does voltage drop as you go around a circuit, through each component?
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Yes! From positive to negative it will drop through each component with some resistance (bulbs, motors etc.)
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What happens to three bulbs connected in series
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They all are equally dimmed as voltage drops and all get 1/3 current
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What happens to three bulbs in parallel
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they are all equally bright. Each bulb gets full voltage and current
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