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Electricity part 2
| Question | Answer |
|---|---|
| What is charge measured in? | Charge is measured in coulombs. |
| What instrument is used to measure electric current? | An ammeter. |
| How is an ammeter connected in a circuit? | In series. |
| What instrument is used to measure potential difference? | A voltmeter. |
| How is a voltmeter connected in a circuit? | In parallel. |
| What instrument is used to measure resistance? | An ohmmeter. |
| Why must a circuit be closed for current to flow? | Because charges need a complete path. |
| What happens to resistance when the length of a wire increases? | Resistance increases. |
| What happens to resistance when the cross-sectional area of a wire increases? | Resistance decreases. |
| How does temperature affect the resistance of a metal? | Resistance increases as temperature increases. |
| What is an I–V characteristic? | A graph showing the relationship between current and voltage. |
| What does a straight-line I–V graph through the origin show? | The conductor obeys Ohm’s Law. |
| What is a non-ohmic conductor? | A conductor that does not obey Ohm’s Law. |
| Give an example of a non-ohmic device | A filament lamp. |
| Why does a filament lamp not obey Ohm’s Law? | Its temperature changes as current increases. |
| What is internal resistance? | Resistance inside a cell that reduces terminal voltage. |
| What is terminal voltage? | The potential difference across the terminals of a cell. |
| What causes energy loss in transmission lines? | High current causing heating. |
| How can energy loss in cables be reduced? | By using high voltage and low current. |
| What is the purpose of a switch in a circuit? | To open or close the circuit. |
| Why are household appliances connected in parallel? | So they receive full voltage and work independently. |
| What happens if one appliance fails in a parallel circuit? | Other appliances continue working. |
| Why is a fuse made of thin wire? | So it heats up and melts quickly. |
| Why is earthing important in homes? | To prevent electric shock. |
| What happens when a live wire touches a metal case? | Current flows to earth instead of through a person. |
| What is an electric shock? | The passage of current through the human body. |
| Why is water dangerous around electricity? | Water conducts electricity. |
| What is electrostatics? | The study of stationary electric charges. |
| What is charging by friction? | Charging by rubbing two materials together. |
| What is charging by conduction? | Charging by direct contact. |
| What is charging by induction? | Charging without direct contact. |
| Why do balloons stick to walls after rubbing? | Because of electrostatic attraction. |
| What material is attracted by magnets? | Magnetic materials like iron. |
| What materials are non-magnetic? | Materials like wood, plastic, and copper. |
| What happens when a magnet is cut in half? | Each piece becomes a magnet with two poles. |
| Can magnetic poles be isolated? | No, magnetic poles always exist in pairs. |
| What is magnetic flux? | The amount of magnetic field passing through an area. |
| What shows the direction of a magnetic field? | A compass needle. |
| What happens to magnetic field lines near the poles? | They are closer together. |
| What does the closeness of field lines indicate? | Field strength. |
| What is a solenoid? | A coil of wire that produces a magnetic field when current flows. |
| What happens when current flows through a solenoid? | It behaves like a bar magnet. |
| What rule gives the direction of magnetic field around a conductor? | The right-hand grip rule. |
| What happens when current increases in a solenoid? | The magnetic field becomes stronger. |
| Why is soft iron used in electromagnets? | It magnetises and demagnetises easily. |
| What is the advantage of an electromagnet over a permanent magnet? | It can be switched on and off. |
| What effect does a magnetic field have on a current-carrying conductor? | It experiences a force. |
| What rule predicts the direction of force on a conductor? | Fleming’s left-hand rule. |
| What is the motor effect? | The force on a current-carrying conductor in a magnetic field. |
| What happens if the current direction is reversed? | The force direction reverses. |
| What happens if the magnetic field direction is reversed? | The force direction reverses. |
| What is electromagnetic induction caused by? | Relative motion between a conductor and a magnetic field. |
| What rule gives the direction of induced current? | Fleming’s right-hand rule. |
| What factors affect the size of induced emf? | Speed, magnetic field strength, and number of turns. |
| What is a step-up transformer? | A transformer that increases voltage. |
| What is a step-down transformer? | A transformer that decreases voltage. |
| Why do transformers only work with AC? | Because a changing magnetic field is required. |
| What is the function of the core in a transformer? | To concentrate the magnetic field. |
| Why is the transformer core laminated? | To reduce energy loss by eddy currents. |
| What is mains electricity? | Electricity supplied to homes. |
| What is the frequency of AC mains supply? | The number of cycles per second. |
| What unit is frequency measured in? | Hertz (Hz). |
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