Electromagnetic Induction - Grade 10

A set of fill-in-the-blank flashcards covering key concepts from the electromagnetic induction lecture notes.

EM induction is the process of generating an electromotive force (voltage) or current in a conductor by exposing it to a changing __.

magnetic field

The discovery of electromagnetic induction was made by Michael Faraday in .

1831

The potential difference between any two points in a conductor is known as induced __.

emf (electromotive force)

There should be a relative motion between the conductor and the .

magnet

The phenomenon of induction occurs without direct physical contact between the conductor and the magnet; this is called induction.

electromagnetic

When a conductor moves through a changing magnetic field, the free electrons experience a force and move to produce an induced .

current

In a fixed magnetic field, if a conductor cuts the field lines as it moves, an emf is induced in the .

wire

When a magnet moves through a coil, the magnetic field lines cut through the turns, inducing an emf in the coil. A voltmeter can be used to measure the size of the .

emf

The direction of the induced emf always opposes the change that causes it (Lenz's Law). The law states that the direction of an induced emf .

opposes

If a magnet is pushed into a coil north end first, the end of the coil closest to the magnet becomes a pole.

north

If a magnet is pulled away from a coil, the end of the coil closest to the magnet becomes a pole.

south

Right-Hand Dynamo Rule: the first finger indicates the direction of the magnetic field, the second finger the direction of the current, and the thumb indicates the direction of the .

motion

Fleming's Left-Hand Rule: the thumb indicates the direction of the force, the first finger the direction of the magnetic field, and the second finger the direction of the .

current

An alternating current is produced by an generator.

AC (a.c.) or a.c. generator

A simple a.c. generator consists of a rotating coil of wire between the poles of a permanent magnet, slip rings and .

brushes

A maximum emf is induced when the coil is in a position and moving perpendicular to the field.

horizontal

No emf is induced when the coil is in a position and the motion is parallel to the field.

vertical

The graph of emf against angle for an AC generator starts as a cosine curve if the coil starts at a position.

horizontal

If the coil starts from a vertical position, the emf-time graph is a curve.

sine

One factor that increases emf is increasing the number of on the coil.

turns

Increasing the area of the coil increases the induced emf because there is more wire to cut through the .

magnetic field lines

The strength of the magnetic field: increasing it increases the induced emf; this is because there are more magnetic field lines in a given .

area

To increase emf in an AC generator, you can increase the frequency of rotation, the number of turns, the strength of the magnet, or insert a soft iron core into the coil. One method is increasing the frequency of of the coil.

rotation

The number of turns on the coil: increasing the turns increases the size of the induced .

emf

The size of the coils: increasing the area increases the emf by providing more wire to cut through the magnetic field lines; this is related to the coil's .

area

The strength of the magnetic field: increasing it increases the size of the induced emf because there are more field lines in a given .

area

The right-hand grip rule can be used to determine the direction of the magnetic field around a straight current-carrying wire; the field lines form around the wire.

concentric circles

Around a straight current-carrying wire the magnetic field lines are circular and have no .

poles

The direction of the magnetic field around a current-carrying wire can be determined using the grip rule.

right-hand

In a solenoid, the magnetic field lines are similar to a bar magnet; the north pole forms at the end where the current flows , and the south pole at the end where the current flows clockwise.

anti-clockwise

In a solenoid, the north pole forms at the end where the current flows anti-clockwise, and the south pole at the end where it flows .

clockwise

A current-carrying conductor experiences a force only if the current is perpendicular to the direction of the magnetic lines.

field

Fleming's left-hand rule: the thumb points in the direction of the force, the first finger in the direction of the magnetic field, and the second finger in the direction of the .

current

A relay consists of an electromagnet and a switch; when current flows through the coil in Circuit 1, it attracts the switch in Circuit 2, closing it to allow current to flow in Circuit 2. The component that provides the driving magnetic field is the .

electromagnet

Electric bells operate by repeatedly moving an armature and breaking the circuit; this causes the hammer to strike the bell and the process to again.

restart or repeat (break is acceptable depending on phrasing)

Loudspeakers work due to the motor effect; a coil and a permanent magnet cause the coil to and produce sound waves.

oscillate

To visualize magnetic fields around a wire, you can use plotting compasses or filings.

iron

When current is reversed in plotting compasses, the field direction .

reverses

Experiment 1: Moving a magnet through a coil shows that an emf is induced only when there is motion between the magnet and coil.

relative

Experiment 2: Moving a wire through a magnet demonstrates that emf is induced when the wire moves between the magnetic .

poles

The magnetic field around a straight wire forms circles around the wire.

concentric

The magnetic field strength around a straight wire increases with increasing current and decreases with distance from the wire; when current changes, the field direction also .

reverses

In an electromagnet, inserting a soft iron core into a solenoid increases the overall magnetic .

strength

Electromagnets are used in relays, electric bells, and to convert electrical signals into sound.

loudspeakers

The direction of the force on a current-carrying wire in a magnetic field can be determined using 's left-hand rule.

Fleming

The graph of emf against angle in an AC generator completes a full cycle after 360°; this is called one .

cycle