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Physics Unit 3 > Generating electricity > Flashcards

Generating electricity Flashcards

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1
Q

Electromagnetic induction

A

electromagnetic induction is the production of an electromotive force (EMF) due to the change in magnetic flux through a conducting loop

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2
Q

electromotive force (EMF)

A

The voltage created or supplied due to energy being transformed into electrical potential energy

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3
Q

Magnetic flux

A

magnetic flux a measure of the amount of magnetic field lines passing through an area

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4
Q

Magnetic flux density

A

magnetic flux density is the amount of magnetic flux per unit area. Equivalent to magnetic field strength

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5
Q

Induced current

A

the induced current is the current produced in a conductor due to a changing magnetic field

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6
Q

AC (alternating current)

A

AC (alternating current) electricity is electricity with a periodically alternating direction of current and voltage

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7
Q

Alternator

A

Alternator a device that transforms kinetic energy into AC electricity by electromagnetic induction; an AC generator

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8
Q

Amplitude

A

amplitude is the magnitude of the maximum variation of any quantity with a changing value

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9
Q

DC (direct current electricity)

A

DC (direct current) electricity is electricity with a constant direction of current and voltage

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10
Q

Frequency

A

frequency is the number of cycles completed per unit of time

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11
Q

Generator

A

A generator is a device that transforms kinetic energy into (either AC or DC) electricity by electromagnetic induction

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12
Q

Period

A

period is the time taken to complete one cycle

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13
Q

Slip rings

A

slip rings s a component used to maintain a constant electrical connection between a stationary external circuit and a rotating coil

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14
Q

Slip ring commutator

A

A split ring commutator is a component used to reverse the electrical connection between a stationary external circuit and a rotating coil every half rotation

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15
Q

What is the formula to calculate magnetic flux when the magnetic field is perpendicular to the area

A
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16
Q

What is the effect of the angle between the magnetic field and the magnetic flux?

A

Magnetic flux is a maximum when the given area is perpendicular to the magnetic field.

When the area is not perpendicular, the effective area is reduced because fewer magnetic field lines pass through it.

If the area is parallel to the magnetic field, the effective area is zero so the magnetic flux will be zero.

17
Q

Faraday’s law

A

States that a changing magnetic flux in a conducting loop or coil induces an electromotive force (equivalent to a voltage) with a magnitude that is proportional to the rate of change of the magnetic flux.

18
Q

What is the formula to find the electromotive force (EMF)?

A
19
Q

What does the negative sign in faradays law indicate?

A

The negative sign in Faraday’s law indicates the direction of the induced EMF and current. which can be disregarded in VCE physics

20
Q

What can be found from Magnetic flux vs time graphs (Ø vs t) and EMF vs time graphs

A

The EMF is equal to n x the gradient of the graph.

The EMF graph should be negative when the magnetic flux graph has a positive gradient and vice versa.

21
Q

Lenz Law

A

Lenz’s law states that when a conductor experiences a change in magnetic flux, a current will be induced such that its magnetic field acts to oppose the initial change in magnetic flux.

22
Q

How do identify the flux through a loop?

A
  • the area of the loop within the magnetic field is increasing or decreasing.
  • the strength of the magnetic field within the loop is increasing or decreasing.
23
Q

What does Lenz law state?

A

an induced current will flow in a direction such that the magnetic field created by the current will oppose the change in flux that induced the current.

24
Q

The four steps involved determining the direction of the induced current.

A
  1. Identify whether the magnetic flux is increasing or decreasing.
  2. Identify the direction of the current
  3. Identify the direction of the induced magnetic field

4 Apply the right-hand coil rule, with the thumb pointing in the direction of the induced magnetic field identified in step 3, to determine the direction of the induced current.

25
Q

What is flux also thought of?

A

Flux can be thought as the number of lines that pass through a magnetic field

26
Q

The formula for calculating magnetic flux

A

Φ = BTxA

Φ is magnetic flux and measured in (Wb), B is the magnetic field strength (T) and A is the area perpendicular to the magnetic field.

27
Q

Generator

A

A generator is a device that uses a rotating coil within a magnetic field to generate electricity.

28
Q

Graph a Magnetic flux and EMF for alternators

A
29
Q

What are the important features of Magnetic flux and EMF graph? (Magnetic flux time graph)

A
  • The flux is zero whenever the coil is parallel to the magnetic field.
  • The magnitude of the flux is a maximum whenever the coil is perpendicular to the magnetic field.
  • A negative flux indicates that the magnetic field lines are passing through the coil in the opposite direction, relative to the coil, to a positive flux. The choice of which direction is positive is not important, but we must be consistent.
  • The flux varies sinusoidally with time.
30
Q

What are some important features of EMF-time graphs?

A
  • The EMF is zero whenever the magnitude of the flux is a maximum (when the coil is perpendicular to the magnetic field).
  • The magnitude of the EMF is a maximum whenever the flux is zero (when the coil is parallel to the magnetic field).
  • The EMF has a positive value whenever the flux is decreasing (negative gradient) and it has a negative value whenever the flux is increasing (positive gradient).
  • The EMF varies sinusoidally with time. The maximum value of the EMF graph occurs one-quarter of a cycle later than the maximum value of the magnetic flux.
31
Q

Sinusoidal

A

having the form of a sine curve.

32
Q

The formula for finding the frequency of sinusoidal waves.

A

f = 1/T

f = frequency (Hz), T = period (s)

33
Q

If the speed of the rotation is increased how will it will affect the frequency, period, and amplitude of the EMF?

A
  • The number of full rotations of the coil per second increases, so the frequency increases.
  • The time taken to complete one full rotation decreases, so the period decreases.
  • The rate of change of flux through the coil increases, so the EMF amplitude increases
34
Q

What is the difference between the DC generators and alternators?

A

The only difference in the apparatus between DC generators and alternators is that a split-ring commutator is used in DC generators whereas slip rings are used in alternators.

35
Q

What is the difference between the function of a DC generator and an alternator?

A

The only difference between the function of a DC generator and an alternator is that a DC generator produces a voltage output in a constant direction (a rectified sinusoid) whereas an alternator produces an AC output.

36
Q

Ohms law formula

A

V=RI

V=voltage, R=resistance, I= current

37
Q
A

Physics Unit 3 (7 decks)

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