magnetism Flashcards
What is electromagnetic induction?
Electromagnetic induction is when a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it.
What is the generator effect?
The generator effect refers to the induction of current in a conductor when it moves through a magnetic field, without any initial current present.
What is the motor effect?
The motor effect occurs when there is already a current in the conductor which experiences a force in a magnetic field.
What induces a potential difference in a conductor?
A potential difference is induced in a conductor if there is relative movement between the conductor and the magnetic field.
How can a potential difference be induced in a wire?
By moving the wire through a magnetic field, cutting through the field lines.
What happens when a magnet moves through a coil?
The field lines cut through the turns on the coil, inducing a potential difference in the coil.
Which instrument can measure the induced potential difference?
A sensitive voltmeter.
What factors affect the induced potential difference?
The size of the induced potential difference is determined by:
* The speed of movement
* The number of turns on the coils
* The size of the coils
* The strength of the magnetic field
How does increasing the speed of the conductor affect the induced potential difference?
Increasing the speed will increase the rate at which the magnetic field lines are cut, thus increasing the induced potential difference.
What is the effect of increasing the number of turns on the coils?
Increasing the number of turns will increase the potential difference induced.
What happens if the length of wire is reduced while maintaining the number of turns?
The potential difference induced will increase because each coil will cut through the magnetic field lines.
How does the size of the coils affect the induced potential difference?
Increasing the area of the coils will increase the potential difference induced.
What is the relationship between the strength of the magnetic field and the induced potential difference?
Increasing the strength of the magnetic field will increase the potential difference induced.
How does the orientation of the poles of the magnet affect the induced potential difference?
Reversing the direction in which the wire, coil, or magnet is moved will change the direction of the induced potential difference.
What is an alternator?
An alternator is a type of generator that converts mechanical energy to electrical energy in the form of alternating current.
What is the main component of a simple alternator?
A rotating coil in a magnetic field with slip rings.
What happens when the coil in an alternator turns?
The pointer deflects first one way, then the opposite way, and then back again due to the alternating potential difference induced.
How is alternating current produced in an alternator?
By the coil cutting through the magnetic field lines or when a magnet rotates within a stationary coil.
What is a dynamo?
A dynamo is a direct current generator that also uses a rotating coil in a magnetic field.
What distinguishes a dynamo from an alternator?
A dynamo has a split-ring commutator instead of two separate slip rings.
What does the split-ring commutator do in a dynamo?
It changes the connections between the coil and the brushes every half turn to keep the current in the same direction.
What is the output current type from a dynamo?
The output current from a dynamo is direct current (D.C.).
True or False: Motors and generators perform the same function.
False.
Fill in the blank: The key principle for generating alternating current is the ______ between the coil and the magnet.
[relative motion]
What is the primary function of a dynamo?
To convert mechanical energy into electrical energy.
True or False: An alternator produces direct current (DC).
False.
What is the main difference between a dynamo and an alternator?
A dynamo produces direct current (DC) while an alternator produces alternating current (AC).
What is the primary function of an alternator?
To convert mechanical energy into electrical energy.
True or False: A dynamo produces alternating current (AC).
False; a dynamo produces direct current (DC).
Fill in the blank: An alternator uses ________ to generate electricity.
electromagnetic induction
Which type of current does an alternator produce?
Alternating current (AC).
What is the role of the stator in a dynamo?
To create a rotating magnetic field.
Multiple choice: Which of the following is a key difference between dynamos and alternators? A) Dynamos are more efficient B) Dynamos produce AC C) Alternators produce AC
C) Alternators produce AC.
True or False: Both alternators and dynamos convert mechanical energy into electrical energy.
True.
Short answer: Name one application of alternators.
Used in vehicles to charge the battery.
Fill in the blank: The output voltage of an alternator can be increased by increasing the ________ of the magnetic field.
strength
What type of current does a dynamo produce?
Direct current (DC).
True or False: The efficiency of an alternator is typically higher than that of a dynamo.
True.
What happens to the output voltage if the speed of rotation in an alternator doubles?
The output voltage approximately doubles.
describe how the alternating current generates a sound wave in a loudspeaker (4)
current in coil produces magnetic field
MP2. direction of this magnetic field is (continuously) changing;
MP3. field of coil interacts with field of magnet;
MP4. producing a force on coil/wire;
MP5. direction of the force changes;
MP6. cone/coil/wire vibrates
MP7. air particles (next to the cone) are made to
vibrate;
how is a uniform field made
they need to be parralel with one another
metals suitable for use of permanent magnet
nickel or steel
investigstion to determine shape of the magnetic field around bar magnet
iron filings used;
sprinkled
card tapped (to reveal pattern);
or
(plotting) compass used;
multiple compasses or repeated use of single
compass;
joining up of dots/idea of compasses forming
continuous line;
why does coil rotate when there is a current in the coil
current / coil has a magnetic field;
interaction between fields;
resulting in a force;
forces on opposite sides of the coil are in opposite
directions;
