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# Chapter 13, 14

### Revise Current Electricity

Question | Answer |
---|---|

What is an electric current? | A electric current it the flow of electricity. |

What unit is current measured in? | Ampere (Amps). |

What is the symbol for current? | A. |

What instrument measures current? | Ammeter. |

What is potential difference or voltage? | Voltage or potential is the electric energy charge difference of electric potential energy transported between two points. |

What unit is voltage measured in? | Volts. |

What is the symbol for voltage? | V. |

What instrument measures voltage? | Voltmeter. |

What is resistance? | Resistance is the opposition to the passage of electrical current. |

What unit is resistance measured in? | Ohms. |

What is the symbol for resistance? | Ω (Ohm/Greek letter Omega) |

What instrument measures resistance? | Ohmmeter. |

What is the function of the following components in a circuit? Battery, switch, resistor, voltmeter, ammeter. | Battery: Supplies the electricity. Switch: Turns the circuit on and off. Resistor: Limits the flow of current in the circuit. Voltmeter: Measures the voltage in the circuit. Ammeter: Measures the amps in a circuit. |

What is Ohm’s law? | The current through two point is directly proportional to the voltage difference across the two points. |

What is the formula for Ohm’s Law? | Current (I) is equal to Voltage (V) over Resistance (R), I=V/R |

What is meant by a series circuit? | When all the parts of the circuit are connected end to end as a single electrical path. |

Explain what happens if one bulb in the series circuit blows. | All the other bulbs stop lighting. |

What is meant by a parallel circuit? | When all the parts of the circuit are connect to each other but through multiple paths. |

Explain what happens if one bulb in the parallel circuit blows. | The other continue to work as the electricity can still flow around the circuit. |

What is direct current? | Current that flows only in one direction. |

What is alternating current? | Current that switches direction rapidly. |

What is the voltage of the mains supply? | 220-240V (230V). |

What is the unit of electricity? | Kilo Watt hour KWh. |

An electrical kettle has a power rating of 2kW, and is used to boil water for three hours every day. What is the cost of running the kettle for a week? | 42kWh. |

Explain the role of the fuse both in a plug and a circuit breaker. | The fuse is a safety mechanism. It stops high current electricity spikes by burning itself out if the current gets too high. |