Module 6: Electromagnetism

Question 1

when is the maximum force produced on a current carrying conductor in a uniform magnetic field

Answer 1

the force on the conductor will be maximum when the conductor is perpendicular to the magnetic field

Question 2

under what conditions is no force produced on a conductor in a uniform magnetic field

Answer 2

the force on the conductor will be zero when the conductor is parallel to the magnetic field

Question 3

what is the relationship between the international system of units (SI) definition of an ampere and Newton’s third law of motion

Answer 3

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Question 4

what is Faraday’s law of induction

Answer 4

the average electromotive force (emf) induced in a conductive loop, in which there is a changing magnetic flux, is proportional to the rate of change of flux

Question 5

what is Lenz’s law

Answer 5

an induced emf always gives rise to a current that creates a magnetic field that opposes the original change in flux through the circuit

induced emf = induced current = induced magnetic field that will oppose the original change in flux

Question 6

what is Lenz’s law

Answer 6

an induced emf always gives rise to a current whose magnetic field will oppose the original change in flux

induced emf = induced current = induced magnetic field that will oppose the original change in flux

Question 7

what is an ideal transformer and what limitations are there for the ideal transformer model

Answer 7

an ideal transformer is an ‘imaginary’ transformer that has no loss in energy. it’s efficiency is 100%
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Question 8

what strategies are used to improve transformer efficiency

Answer 8

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Question 9

what are step up and step down transformers

Answer 9

step up transformer: has more turns in the secondary coil
–> increasing voltage, decreasing current
step down transformer: has more turns in the primary coil
–> decreasing voltage, increasing current

Question 10

what is the process of the production of an electromotive force (emf)

Answer 10

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Question 11

how does relative movement or changes in current in one solenoid in the vicinity of another solenoid generate an electromotive force

Answer 11

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Question 12

what are the functions of the components of a simple DC motor

Answer 12

stator = usually stationary bar magnets that produce a magnetic field

rotor = usually consists of copper wire wound into a coil around an axle. when electric current flows through the coil, the axle spins

commutator = reverses the direction of current in the coil each time the coil rotates half a turn to ensure the axle spins in one direction

brushes = send electrical current t the commutator and are typically made of graphite

Question 13

how is torque produced in a DC motor

Answer 13

in a DC motor, the rotor (coil) carries current. the rotor lies between the stator (magnetic field) and hence will experience a force.
therefore, torque is produced at the circumference of the rotor and the rotor starts rotating

Question 14

what is the motor effect

Answer 14

a current carrying conductor in a uniform magnetic field will experience a force

Question 15

what is back emf and what effect does it have on a simple DC motor

Answer 15

back emf is the induced emf produced by the relative movement of a conductor

it is the electromotive force that opposes the change in current which induced it

Question 16

how does a simple DC generator operate

Answer 16

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Question 17

what is the difference between a DC generator and an AC generator

Answer 17

an AC generator creates an alternating current that periodically reverses direction
in a DC generator, a direct current flows in one direction

Question 18

what is the difference between a DC generator and an AC generator

Answer 18

an AC generator creates an alternating current that periodically reverses direction
in a DC generator, a direct current flows in one direction

Question 19

how does a simple AC generator operate

Answer 19

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Question 20

what is the relationship between lenz’s law and the law of conservation of energy

Answer 20

lenz’s law ensures that the mechanical energy of the wire is reduced by the same amount of electrical energy gained (by the induced current) so that the law of conservation of energy is not violated
it does this by exerting a force on the wire opposing the wire’s motion. this causes the wire to lose mechanical energy

Question 21

how does the law of conservation of energy apply to DC motors

Answer 21

a DC motor will generate a back emf when running normally as a result of an induced current produced in response to the rotation of the rotor inside the motor in the presence of an external magnetic field

Question 22

what is magnetic braking

Answer 22

magnetic braking occurs where the electromagnetic force between a magnet and a conductor in motion is used to create a repulsive and slowing force

eddy currents create their own magnetic field that opposes the original magnetic field of the magnet

this creates a drag force between the magnet and the conductor which slows the conductor down

Question 23

how does the law of conservation of energy apply to magnetic braking

Answer 23

THIS CARD IS NOT DONE