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Copiado por Robin Skailes
hace más de 6 años
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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. |
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| Draw the I-V Characteristic graph for a filament lamp. |
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| Draw the I-V characteristic graph of a diode. |
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Explain the following I-V Characteristic graph.
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The current through an ohmic conductor is directly proportional to the potential difference provided that there is a constant temperature. |
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Explain the following I-V characteristic graph.
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As the current increases, so does the temperature of the filament which increases resistance. Less current will be able to flow hence the curve. |
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Explain the following I-V characteristic graph.
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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. |
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Explain how, in this circuit, as the room gets warmer the fan would spin faster.
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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. |
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In the following circuit, what would happen if a bulb was disconnected or removed?
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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. |
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Calculate the total current passing through the circuit shown on the left.
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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] |
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| 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] |
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| Draw a graph showing how the number of resistors connected in a circuit changes the resistance in series. |
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| Draw a graph showing how the number of resistors connected in a circuit changes the resistance in parallel. |
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| 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] |
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| 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. |
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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]
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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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