P2 - Flashcards - Electricity

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GCSE Physics Fichas sobre P2 - Flashcards - Electricity, creado por Robin Skailes el 18/06/2018.
Robin Skailes
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Pregunta Respuesta
What is current? Current is the flow of electrical charge.
What is required for current to flow around a complete circuit? A source of potential difference.
Describe the current in a series circuit? It will be the same at any point in the circuit.
What is another name for potential difference? Voltage
What is the unit of current? Ampere. (A)
What is the unit of potential difference? Volt (V)
What is resistance? Anything that slows the flow of current.
What is the unit of resistance? Ohm (Ω)
How does the level of resistance affect the current in a circuit? The more resistance there is across a component, the smaller the current is.
What is charge? Charge is the size of the current.
What is charge measured in? Coulombs (C)
How do you calculate charge? Q = It Charge = Current x Time
A battery charger passes a current of 2A through a cell for 2.5 hours. How much charge is transferred to the cell? 18,000 Coulombs (2x(2.5x60x60))
How could I get more charge to pass through a circuit? By increasing the amount of current.
What is the following circuit symbol? Cell
What is the following circuit symbol? Battery
What is the following circuit symbol? Open switch
What is the following circuit symbol? Closed switch
What is the following circuit symbol? Bulb/Lamp
What is the following circuit symbol? Fuse
What is the following circuit symbol? LED Light emitting Diode
What is the following circuit symbol? Resistor
What is the following circuit symbol? Variable resistor
What is the following circuit symbol? Ammeter
What is the following circuit symbol? Voltmeter
What is the following circuit symbol? Diode
What is the following circuit symbol? LDR Light dependant resistor
What is the following circuit symbol? Thermistor
What is the formula which links potential difference and current? V = IxR Potential difference = Current x Resistance.
A 4Ω resistor has a potential difference of 6V across it. What is the current flowing through the resistor? 1.5A 6 / 4 = 1.5
Name three factors that affect resistance in a circuit. Components in series or parallel, length of wire, thickness of wire or temperature of the wire.
What is this experiment trying to explore? How the length of a piece of wire impacts the resistance of the wire.
What are the two components which are not labelled? Batteries and a Switch
What does this graph tell you about the resistance of a wire? The resistance is directly proportional to the length of the wire.
Susie's graph doesn't pass through the origin. Suggest a reason why this might be? It could be because the first crocodile clip wasn't placed exactly on zero throwing the results off slightly.
What is the answer to the following question? r = v/i [1 mark] 230/5 [1 mark] 46Ω [1 mark]
Describe the resistance of an ohmic conductor. The resistance will not change with the current.
Describe the relation between the current and potential difference of an ohmic conductor. Provided there is a constant temperature, the current
Describe what happens when an electrical charge runs through a filament lamp. Some energy is transferred to the thermal energy store of the filament which heats up. As resistance is affected by temperature, the resistance increases with the temperature.
Describe the resistance of a diode. It depends on the direction of the current. Current can easily flow in one direction but there is a large resistance in the other direction.
Explain why diodes are used in phone chargers. Because the alternating current is unable to flow out of the phone after it enters, it means that the phone can charge.
Draw the I-V characteristic graph for an ohmic conductor.
Draw the I-V Characteristic graph for a filament lamp.
Draw the I-V characteristic graph of a diode.
Explain the following I-V Characteristic graph. The current through an ohmic conductor is directly proportional to the potential difference provided that there is a constant temperature.
Explain the following I-V characteristic graph. As the current increases, so does the temperature of the filament which increases resistance. Less current will be able to flow hence the curve.
Explain the following I-V characteristic graph. Current will only flow in one direction in a diode because in the reverse direction there is a high level of resistance.
What does LDR stand for? Light dependant resistor.
Describe how a LDR works. It alters the resistance depending on the light level. With increased light there is decreased resistance and with decreased light there is increased resistance.
Give 2 examples as to the applications of LDRs. Automatic Night Lights, Outdoor lighting, burglar alarms.
Describe how a thermistor works. It alters the resistance depending on the heat level. With increased heat there is decreased resistance and with decreased heat there is increased resistance.
Explain how, in this circuit, as the room gets warmer the fan would spin faster. As the room gets warmer, the resistance of the thermistor decreases and gets a smaller share of potential difference. Therefore the pd share the other two increases making the fan go faster.
Describe how a series circuit would be connected. Everything would be connected in a line, one after another, between the two sides of the power supply.
In the following circuit, what would happen if a bulb was disconnected or removed? The entire circuit would cease to function.
Describe the potential difference in series circuits. The potential difference of the power supply is shared between the components of a circuit.
Describe the current in a series circuit. It is equal at any point in the circuit.
Describe the resistance of two components in a series circuit. They will add up to the total resistance of the circuit.
Calculate the total current passing through the circuit shown on the left. 2Ω + 3Ω = 5Ω I = V ÷ R I = 20 ÷ 5 I = 4A
In a circuit there are two cells each with a voltage of 1.1 volts. What is the total potential difference of the circuit? 2.2 Volts
2 12 V cells are connected in series with a 3Ω resistor, a 2Ω resistor and a 7Ω resistor. Calculate the current passing through the circuit. [5 marks]
Describe the potential difference in a parallel circuit. It is equal across all components.
Describe the current in a parallel circuit. The current is shared amongst branches.
What happens if you add a resistor in a parallel circuit? The overall resistance goes down.
Explain what happens to the current and resistance in a circuit with a cell and a resistor, when another resistor is added in parallel? [2 Marks] The current through the resistor increases. [1 mark] The resistance decreases to less than the value of the lowest resistance. [1 mark]
Draw a circuit diagram where 2 bulbs are connected to a battery in parallel. Both lamps should be able to switch on and off without affecting anything else. [3 marks]
Draw a graph showing how the number of resistors connected in a circuit changes the resistance in series.
Draw a graph showing how the number of resistors connected in a circuit changes the resistance in parallel.
Draw a diagram of a single circuit that could be used to investigate the effect of adding resistors in parallel. Your circuit should include switches. [1 mark]
Name the two types of electricity supply. Alternating current / AC Direct Current / DC
Describe the current in the UK mains supply. It is alternating current. Has a p.d of 230v Has a frequency of 50 Hz
Compare AC and DC current. AC constantly changes direction and is produced by alternating voltages. DC always flows in the same direction and is created by a direct voltage.
Describe the structure of a three core cable. They have three wires inside of them each with a copper core and a coloured plastic coating.
Name the three wires in a standard UK cable. Live Neutral Earth
What colour are the three wires in a standard cable? Live - Brown Neutral - Blue Earth - Green and Yellow
Describe the purpose of the live wire. The live wire provides the alternating p.d from the mains supply.
Describe the purpose of the neutral wire. The neutral wire completes the circuit and carries away current.
Describe the purpose of the earth wire. It is for protecting the wiring, and for safety. It stops the whole appliance from becoming live. It only carries current when there is a fault.
Explain what would happen if you were to touch the live wire. Your body has a p.d of 0v. If you touch the live wire then a p.d is produced across your body and a current flows through you giving you a potentially fatal electric shock.
What could happen if there was a connection between the live an neutral wires? It could create a low resistance path to the earth causing a huge current to flow which could result in a fire.
State the potential difference of: The live wire, The neutral wire, The earth wire. [3 marks] 230v - live 0v - neutral 0v - earth [1 mark each]
Write the equation for energy transferred. E = Pt Energy transfered (j) = Power (w) x time (s)
A 600w microwave is used for 5 minutes. How long in minutes would it take a 750w microwave to do the same amount of work? 4 minutes. Calculate the energy transferred by the first microwave. re-arrange the equation and find out the time using the energy transferred and power.
A circuit is made up of just a 10 Ω resistor. Explain why there is no current in the circuit. [1 mark] There is no source of potential difference.
The diagram shows an ammeter . It has a reading of 0.5A. If another ammeter was placed at point x, what would the reading be? [1 mark] 0.5A
A current of 3A flows through a 6Ω resistor. Calculate the potential difference of the circuit. [2 marks] V = IR V = 3x6 [1 mark] V = 18 [1 mark]
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