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PHYSICS > Electricity and Magnetism > Flashcards

Electricity and Magnetism Flashcards

1
Q

field of force

A

a region in which test particles experience a force

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2
Q

what are electric fields

A

a region in which charged particles experience a force

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3
Q

properties of field lines

A
  1. start from positive end at negative
  2. leave and arrive at charged surface
  3. do not intersect
    4.spacing between field lines indicates strength
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4
Q

uses of electrostatics

A
  • lightning rods
  • in printers of photocopiers
  • in paint spraying
  • in electrostatic precipitators
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5
Q

what is a magnetic field?

A

a region which magnetic materials and moving charges experience a force

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6
Q

soft and hard magnetic materials

A

SOFT - easily magnetised and demagnetised used for temporary magnets, iron
HARD - hard to magnetise and demagnetise, steel , other iron alloys

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7
Q

electric current

A

rate of flow of charge

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8
Q

what are ammeters and how are they connected?

A

device used to measure current
- they are connected in series

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9
Q

electro-motive force

A

any form of energy converted into electrical energy per unit charge

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10
Q

potential difference

A

energy lost per unit charge, by charge as it passes through a conductor

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11
Q

what are voltmeters and how are they connected?

A

device used to measure voltage
- they are connected in parallel

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12
Q

voltage

A

work done per unit charge
voltage
= energy, E / charge, Q

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13
Q

electrical resistance

A

the ratio of the p.d. across the terminals of the conductor to the current flowing through it

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14
Q

resistor

A

an electrical device or component that varies a current and voltage in a circuit

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15
Q

direct current

A

charge flows in one direction

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16
Q

alternating current

A

a type of electrical current where the direction of the flow of electrons switches back and forth at regular intervals or cycles

17
Q

rectification

A

process of converting alternating current to direct current by use of a diode which allows current to flow in one direction

18
Q

solenoid

A

consists of many loops bounded together

19
Q

transformer

A

device used to step up and down voltage

20
Q

types of transformers

A
  1. step up
    increases output voltage
  2. step down
    decreases output voltage
21
Q

transformer equations

A

Vp / Vs = Np / Ns
power in primary = power in secondary

IpVp = IsVs

22
Q

use of a cell or a battery?

A

used to provide electric power to a circuit

23
Q

use of a switch?

A

to control the flow of electricity

24
Q

NB:

A

filament lamps are small bulbs

25
Q

use of a fuse?

A

to protect electrical equipment from excessive current and prevent short circuits

26
Q

use of a diode?

A

only allow current to flow in one direction

27
Q

what is a LED? + examples

A

light-emitting-diode which emits light when current flows through in a forward direction
- alarm clocks
- traffic lights
- LED bulbs

28
Q

use of a fixed resistor?

A

to control or limit the flow of electrical current in a circuit

29
Q

use of a variable resistor?

A

to adjust the value of voltage in a circuit by changing the resistance and keeping the current the same

30
Q

what is an LDR? + example

A

a type of resistor which changes its resistance when light is shone on it
more light = decreased resistance so lots of current can flow
less light = increased resistance less current can flow
- automatic night lights
- burglar alarms

31
Q

what is a thermistor? + example

A

a type of resistor which changes its resistance when it is heated up
- car engines
- electronic thermostats

32
Q

what is Lenz law?

A

The induced potential difference always opposes the change that produces it

33
Q

what is faradays law?

A

the magnitude of the induced e.m.f. is directly proportional to the rate of change of the magnetic flux linkage

34
Q

how to increase induced e.m.f

A
  • increase the rate of movement of the conductor/ magnet
  • increase the number of turns that are being cut by the magnetic field
  • increase the surface area of the coil
  • use a stronger magnet
35
Q

use of Flemings right hand rule?

A

to determine the direction of the induced current

36
Q

factors affecting resistance

A
  • length of the conductor : longer it is higher resistance R∝L
  • cross-section area : smaller it is higher resistance R∝L/A
  • temp. : higher it is higher resistance
    nature of material : certain materials have higher resistance compared to others
37
Q

equation for resistivity of a wire

A

length = R∝L
cross-section area = R∝L/A
diameter = R∝1/d^2
R = k L/A or R = K 1/d^2

38
Q
A

PHYSICS (6 decks)

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