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Magnets
| Question | Answer |
|---|---|
| Define a magnetic field and what is another term for it. | a region of space in which an isolated north pole would experience a force. Magnetic flux density. (B) |
| What is the unit for magnetic field? | Tesla (T) |
| Define Magnetic flux density. | at a point in space is a vector quantity, whose magnitude is equal to the magnitude of the force experienced, by a I carrying conductor, of 1 m with a I of 1 A flowing through it and whose direction is the direction of the force experienced by an isol |
| Define 1 Ampere | 1 amp is the constant current when 2 straight infinitely long parallel conductors are 1 meter apart, in a vacuum, with negligible cross-sectional area; experience a force between them of 2x10^-7 N/m |
| Define Magnetic Flux and its unit | The number of magnetic field lines passing through a surface. Weber (Wb). (Φ ) |
| Define the right-hand rule | This states that if the right-hand clasps a conductor with the thumb pointing in the direction of the current, then the fingers give the direction of the magnetic field around the conductor |
| Define what a solenoid is. | it is a coil whose length is much longer than its radius |
| what is an electromagnet? | if a solid iron core and a solenoid experiences a current passing through the solenoid, the core becomes magnetised |
| define magnetic declination and give it another name. | the angle between true north and magnetic north at a point on the Earth is called magnetic declination or the magnetic variation at that point. |
| Give 4 uses of an electromagnet | powerful electromagnet lifts scrap iron or metal in a scrap yard, relays, electrical machines e.g., transformer and loudspeakers |
| Define a current carrying conductor in a magnetic field and its properties | it will always experience a force unless the conductor is parallel to the magnetic field. The direction of the force is always: perpendicular to the current and perpendicular to the magnetic field. |
| Define Fleming's left-hand rule | it states the if the thumb, first finger and second finger at right angles of the left hand, with the first being the direction of the (B), the second being the direction of the (A), then the thumb in the direction of force (N) |
| What if the current carrying conductor is not perpendicular to the field? | resolve the B into two perpendicular components, one parallel to the conductor and the other at right angles to the conductor |
| How does a charge act in a magnetic field? | If the charged particle moving at a constant speed enters a uniform magnetic field and moves at right angles to the field, the particle moves in a circle |
| Define the coulomb | it is the amount of charge that passes any point in a circuit when a current of 1 Amp flows for 1 second |
| Define electromagnetic induction | whenever the magnetic field passing through a coil changes, an emf appears in the coil |
| Define Weber | if the magnetic flux density over an area of 1m^2 is 1 tesla then the flux through the area is 1 weber |
| State Faraday's Law of electromagnetic induction/ state the first law of electromagnetic induction | it states that the size of the induced emf is directly proportional to the rate of change of flux |
| Define the formula of induced emf | (Final flux-initial flux) ÷ time taken |
| State Lenz's law/ state the 2nd law of electromagnetic induction | states that the direction of an induced current is always such as to oppose the change producing it |
| Give 3 uses of electricity generators | electricity power stations which generate high quantities of electricity, the alternator in a car, the dynamo on a bike |
| electric generator definition | is a device that converts mechanical energy to electrical energy |
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