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45 Cards in this Set
- Front
- Back
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Current
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the rate of flow of charge
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Voltage
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(potential difference) the driving force that pushes the current around the circuit - 'electrical push'
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Resistance
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anything in a circuit which slows down the flow
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what is voltage measured in?
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volts (V)
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what is resistance measured in?
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Ohms (Ω)
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if there is no voltage across a component...
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...the current will not flow through the component
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what is the relationship between voltage, current and resistance?
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-voltage pushes current around
-resistance opposes it -relative sizes of resistance and voltage decide the size of the current |
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if you increase the voltage...
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...more current will flow
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if you increase the resistance...
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...less current will flow/more voltage is needed for the same current
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potential difference
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the energy transferred per unit of charge passed
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when electrons/charge goes through a change in potential difference...
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...energy is released/transferred
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1 volt =
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1 joule per coulomb
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a battery with bigger voltage will...
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...supply more energy per coulomb of charge which flows and therefore, more energy will be lost over the circuit
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what happens to current at a junction?
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it is conserved - no current is lost
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where must the ammeter be placed when measuring the current flowing through a component?
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in series - connected in line with the component
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where must the voltmeter be placed when measuring the potential difference across a component?
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placed in parallel to the component being tested - not around any other component
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what is a V-I graph?
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a Voltage-Current graph
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what happens when you vary the resistance in the variable resistor?
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the current alters
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what does a V-I graph of a fixed resistor look like?
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a straight line with a positive correlation
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why?
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the current through the resistor is proportional to the voltage - linear graph
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what does a V-I graph of a filament look like?
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a curve which is flatter at each end and goes through (0,0) - x cubed graph
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why?
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the temperature increases of the filament and so, the resistance increases
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what does a V-I graph of a diode look like?
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it increases at (0,0) - exponential graph
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why?
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the diode only lets current flow one way
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what is an LDR?
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a light dependant resistor is a special type of resistor which changes its resistance depending on how much light there is
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what is the symbol for an LDR?
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in bright light...
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...resistance falls
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in darkness...
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....resistance is at its highest
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what is a thermistor?
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a special type of resistor which is dependant on temprature
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what is the symbol for a thermistor?
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in hot conditions...
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...resistance falls
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in cool conditions...
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....resistance increases
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why do resistors get hot?
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because the electric current in the resistor causes an energy transfer of heat
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what causes the energy transfer?
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electrons collide with the tightly packed ions which are formed in a lattice in the resistor which in turn gives the ions extra energy which is released as heat
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what does the heating effect cause?
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an increase in the resistance
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what does the increase in resistance cause?
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more current to flow or more voltage supply to maintain the current
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this heating effect can make circuits _____ efficient
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less
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why?
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some energy is wasted as heat
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what else can it cause?
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components can melt and cause the circuit to stop working or not work properly
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what are fuses?
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they protect circuit components by melting and breaking when the current gets too high
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what are 2 things is this heating effect used in as an advantage?
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toasters and light bulbs
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what is electrical power?
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the rate at which an appliance transfers energy
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where does the energy come from?
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the current flowing through it
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An appliance with a high rating will draw a _____ current from the supply
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large
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what is power measured in?
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Watts (W)
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