Topic 13 - Electromagnetic Induction Flashcards

16299134937	how can you produce an electric current using a magnet and conductor?	a changing magnetic field can induce a voltage or potential difference in a wire and this causes a current to flow	0
16299191420	the size of the induced potential difference depends on the	- number of turns in a coil of wire - the strength of the magnetic field - how fast the magnetic field changes or moves past the coil	1
16299251506	a generator	machine that converts mechanical energy into electrical energy - consists of a coil of wire that is rotated inside a magnetic field, as the coil turns, a voltage is induced in the wire -the ends of the coil are connected to slip rings. - electrical contact with an external circuit is made using carbon brushes, which press on the slip rings	2
16299410244	commutator	switches over the connections every half-turn of the coil, and so produces a form of direct current	3
16299419019	dynamo	produces a direct current	4
16299424967	alternator	produces an alternating current	5
16299456499	how does a microphone work?	1) sound waves cause variations in air pressure 2) the pressure variations make a diaphragm vibrate 3) the diaphragm moves a coil of wire backwards and forwards 4) a current is produced	6
16299626970	how does a loudspeaker work?	1) the varying current flows through a coil that is in a magnetic field 2) this causes a force on the coil, which moves backwards and forwards as the current varies 3) the coil is connected to a diaphragm, and the movements of the diaphragm produce sound waves	7
16299877776	step-up transformer	increases the voltage and decreases the current at the same time	8
16299883895	step-down transformer	makes the voltage lower and the current higher	9
16299916970	how do transformers work?	1) a transformer is made using two coils of insulated wire wound onto an iron core - there is no electrical connection between the two coils of wire 2) the alternating current in the primary coil creates a continuously changing magnetic field 3) the iron core of the transformer carries this magnetic field to the secondary coil	10
16299962438	transformers only work with	alternating current	11
16300040562	the potential differences across the coils of a transformer can be worked out using this equation:	potential difference across primary coil / potential difference across secondary coil = number of turns in primary coil / number of turns in secondary coil	12
16300133093	power =	current (A) x potential difference (V)	13
16300196440	power =	energy transferred (J) / time (s)	14
16300210830	power =	current^2 (A) x resistance (ohms)	15
16300165751	potential difference across primary coil (V) × current in primary coil (A) =	potential difference across secondary coil (V) × current in secondary coil (A)	16