6186446
Description
Flashcards by Mel Hughes, updated more than 1 year ago
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Created by Mel Hughes
about 8 years ago
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| Question | Answer |
| What is direct current? | Current that passes in one direction only |
| What is the potential of the neutral terminal? | 0V (volts) |
| Why are the pins of a plug made of brass? | Brass is a good conductor and does not rust or oxidise |
| Why must appliances with metal cases be earthed? | So that the case cannot become live and electrocute you |
| What is a fuse? | A thin wire that heats up and melts if too much current passes through it |
| Why don't appliances with plastic cases need to be earthed? | Plastic is an insulator so it cannot become live |
| What is the power, in kW, of an appliance that transfers 90000J of energy in 30 seconds? | 3kW |
| What is the power of a mains appliance that takes a current of 10A? | 2300W |
| How much charge flows past a particular point in a circuit when a current of 2A flows for 2 minutes? | 240C |
| How much energy is transferred when a charge of 200C flows through a resistor that has a potential difference across it of 230V? | 46000J |
| Why can two-core cable be used for a hairdryer? | The case of the hairdryer is plastic, so it doesn't need an earth |
| Why are filament bulbs very inefficient? | They transfer a lot of energy by heating, rather than as light |
| What is the potential difference of the mains supply? | 230V |
| What is the frequency of the mains supply? | 50 Hz |
| What is the peak voltage of the mains supply? | +/- 325V |
| What colour is the neutral wire? | Blue |
| What does the cover on an earth wire look like? | It has green and yellow stripes |
| Why is the outer cover of a three-pin plug made of plastic? | Plastic is a good electrical insulator |
| What fuse should be used in a 500W mains heater? | 3A |
| What is the unit of charge? | Coulomb, C |
| What is a circuit breaker? | An electromagnetic switch that opens and cuts off the supply if the current is bigger than a certain value |
| How much energy is transferred when a 2kW appliance is used for 15 second? | 30000J |
| What is the current through a 2300W mains heater? | 10A |
| 24000J of energy are transferred when 2000C of charge flow through a bulb. What is the potential difference across the bulb? | 12V |
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