P15 - Electromagnetism Flashcards

1
Q

describe:

permanent magnet

A
  • produces own magnetic field
  • cannot be turned on or off
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2
Q

describe:

induced magnet

A
  • temporary magnet produced when placed in a magnetic field
  • only attracted by other magnets, not repelled
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3
Q

What direction do magnetic field lines act in?

A

North to South

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4
Q

Where is the strongest magnetic field located on a magnet?

A

At the poles

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5
Q

What does the right hand grip rule show?

A

The direction magnetic field lines in concentric circles act in around a wire.

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6
Q

define:

solenoid

A

a coil of wire that produces a uniform magnetic field

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7
Q

desribe:

electromagnet

A

an iron core with a solenoid

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8
Q

list 3:

properties that determine an electromagnet’s strength

A
  • turns in the wire
  • current
  • size of iron core
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9
Q

list 3:

uses of electromagnets

A
  • recycling (sorting materials
  • cranes
  • electric bell
  • relay
  • circuit breakers
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10
Q

What is Flemming’s left hand used for?

A

motors

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11
Q

What does each finger represent in Flemming’s left hand rule?

A

thumb - motion (force)
first finger - magnetic field
second finger - current

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12
Q

formula:

force

on a wire in moters

A

F = BIL
force = magnetic flux density * current * length
N = T * A * m

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13
Q

define:

motor

A

a device that converts electrical energy into kinetic energy

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14
Q

explain:

How speakers work

A

Electromagnetic rod which moves back and forth based on a signal. Vibrations in the cone create pressure waves.

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15
Q

explain:

how an electric bell works

A

Uses an electromagnet to attract an arm to hit the bell. The arm moves and breaks its own circuit causing it to fall. This cycle repeats.

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16
Q

explain:

how a circuit breaker works

A

During a power surge, electromagnet becomes too strong causing a switch to open.

17
Q

split ring commutator

A

switches the polarity of the current every half rotation

18
Q

describe:

DC motor

A
  1. North and south pole magnet around a coil of wire.
  2. Current flows in opposite directions on either side of the coil.
  3. Creates opposite forces that spin the coil due to magnetic forces generated around the wire
  4. When the wire reaches a vertical position (half rotation), the split ring commutator switches the polarity of the current
  5. This causes the forces to be switched and the coil to be pulled down
  6. This means the coil rotates
19
Q

What is Flemming’s right hand rule used for?

A

generators

20
Q

What does each finger represent in Flemming’s left hand rule?

A

thumb - motion (force)
first finger - magnetic field
second finger - current

21
Q

define:

generator

A

a device that converts kinetic energy into electrical energy

22
Q

How common are naturally occuring magnetic materials?

23
Q

define:

elctromagnetic induction

A

production of a voltage when a wire is moved through a magnetic field

24
Q

explain:

elctromagnetic induction

A

A wire moves through a magnetic field so electrons insde the wire move as they align to the magnetic field lines. This induces a voltange, which could generate a current.

25
Q

define:

transformer

A

device that increases or decreases voltage of an AC

26
Q

What does P=IV show about transformers?

A

conservation of energy as voltage is just being converted into current

27
Q

define:

primary and secondary coil

A
  1. primary - input
  2. secondary - output
28
Q

number of turns proportion in a step up transformer

A

more turns on the secondary

taking a ‘step’ up - more

29
Q

number of turns proportion in a step down transformer

A

less turns on the secondary

taking a ‘step’ down - less

30
Q

formula:

number of turns and voltage

in primary and secondary coils

A

Vp / Vs = Np / Ns