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# 7j

### Key Stage 3 Science

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

What is a series circuit? | Contain only one loop and the current is the same |

What is a parallel circuit? | Have branches and the currents in all the branches add up to make the total current |

Draw a series circuit with 1 battery, 1 switch, 1 bulb and an ammeter | |

Draw a parallel circuit with 2 bulbs and a battery | |

What is current and what is its unit and give its symbol? | Current is the flow of electrons. It is measured in amps (A) |

What can be used to measure current in a circuit? | An ammeter |

If the number of bulbs in a series circuit is increased, why does their brightness decrease? | Their brightness will decreases because the current decreases |

What happens to the current if the voltage is increased? | The current will also increase |

What is an electric cell? | A cell gives the electrons energy |

What is voltage? | How much energy each electron has |

What are the units of voltage? | Volts (V) |

How must a voltmeter be connected in order to measure the voltage across a component? | In parallel |

What is resistance? | A way of saying how difficult it is for electricity to flow through something |

What is a fuse? | The fuse breaks the circuit if a fault in an appliance causes too much current to flow. |

What are the two factors that affect the resistance of a wire | 1.The thickness of the wire 2. The length of the wire |

What happens to the current if the thickness of the wire is increased? | It will increase |

What happens to the current if the length of the wire is increased? | It will decrease |

True/False? In a series circuit, the current is the same everywhere | TRUE |

If the number of bulbs in a series circuit is increased, why does their brightness decrease? | Their brightness will decreases because the current decreases |

What happens to the current if the voltage is increased? | The current will also increase |

In an electric cable, what are the colours of the following wires 1.Neutral 2.Live 3.Green-yellow stripes | 1.Blue 2. Brown 3. Earth |

What happens to the current at junctions in a parallel circuit? | The current splits |

What are the units of voltage? | Volts (V) |

How must a voltmeter be connected in order to measure the voltage across a component? | In parallel |

Define "current" | Flow of charge |

Define "potential difference" (or "voltage") | Energy carried by the flow of electrical charge |

State the units of current | Ampere (Amp) |

State the units of potential difference | Volt (V) |

Define "series" circuit | Components in a circuit are all in one loop |

Define "parallel" circuit | Components in a circuit are in separate loops |

Define "resistance" | Slows down the flow of electricity |

State the units of resistance | Ohms |

State the equation used to calculate resistance | R=V/I, Resistance= potential difference/current |

State the equation used to calculate electrical power | P=IV, Power=current x potential difference |

What two things are needed for an electric current to flow | something to transfer energy to electrons (battery), a complete path for the electrons to flow (circuit) |

State the rule for current in a series circuit | The current is the same at every point in the circuit and in every component |

State the rule for potential difference in a series circuit | The total potential difference of the power supply is shared between components |

State the rule for resistance in a series circuit | the more resistors, the greater the resistance. RT=R1+R2 |

State the rule for current in a parallel circuit | The total current through the whole circuit is the sum of the currents through the separate components |

State the rule for potential difference in a parallel circuit | The potential difference across each branch in the circuit is the same |

State the rule for resistance in a parallel circuit | Adding more resistors in parallel decreases resistance |

What is an electrical conductor? | a material that allows charge to move easily through it |

What is an electrical insulator? | material that does not allow charge or heat to pass through it easily |

Compare resistance in electrical conductors and insulators | electrical conductor = low resistance, electrical insulator = high resistance |

How can you investigate how easily a material conducts electricity? | set up a series circuit with a cell, lamp, wires > place material in between two wires > lamp on = conductor |

Give some examples conductors | metal elements, graphite, mixtures of metal, salt solution, liquid calcium chloride |

Give some examples insulators | most non-metal elements (e.g., sulphur, oxygen), diamond, plastic, wood, rock |