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Simon became inarticulate in his effort to express physics' essential illness. > Section 2 - Electricity > Flashcards

Section 2 - Electricity Flashcards

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1
Q

Three types of wire in a plug?

A
  • Live wire(brown)
  • Neutral wire(blue)
  • Earth wire(green/yellow)
  • p18
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2
Q

Metal parts are made of…

A

Copper or brass(good conductors)

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3
Q

The rest of the plug is made of…

A

rubber or plastic(good insulators and flexible)

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4
Q

The live wire

A

-Alternates between high +VE and -VE voltage of about 230V

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5
Q

The neutral wire

A

-Is always at 0V

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6
Q

The earth wire

A
  • Earths the appliance
  • Carries the current away if a fault develops
  • An earthed conductor can never become live
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7
Q

Normal flow of electricity in a plug

A

In through the live wire and out through the neutral wire

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8
Q

How the earth wire and the fuse works

A
  • A fault develops where the live wire touches the metal case
  • A large current flows through the live, through the case, then out down the earth wire
  • The surge melts the fuse(or trips the circuit breaker)
  • This isolates the appliance, making it impossible to get an electric shock
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9
Q

Advantage of a surface breaker

A
  • It opens a switch when a surge is detected
  • This breaks the the circuit
  • Can be easily reset
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10
Q

Resistors

A
  • Heat up when there is an electric current
  • Heat increases the resistance of a resistor
  • Therefore less current will flow
  • This can cause components to melt
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11
Q

Formula for electrical power

A

P = I*V

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12
Q

What is electrical power?

A

Electrical power is the rate at which an appliance transfers energy

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13
Q

What does a higher power rating mean?

A

More energy is transferred in a short time; thus the appliance will draw a large current from the supply

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14
Q

Unit for power

A

watts(W)

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15
Q

Rating of fuses

A

Fuses should be rated as near as possible, but slightly higher than the normal operating current

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16
Q

Formula for energy transferred

A

E = IVt

17
Q

Current

A

The rate of flow of charge round the circuit(A)

18
Q

Voltage

A

The energy transferred per unit charge passed

19
Q

Resistance

A

Anything in the circuit which slows the flow down(Ω)

20
Q

Effect of increasing the voltage

A

More current will flow

21
Q

Effect of increasing the resistance

A

Less current will flow

22
Q

Formula for voltage

A

V = I*R

23
Q

Voltage-current graphs

A

Metal filament lamp - As temperature increases, the resistance increases
Wire - The current through a wire(at constant temperature) is proportional to voltage
Different Resistors - The current through a resistor is proportional to voltage
Diode - Current will only flow through a diode in one direction
p22

24
Q

LEDs

A
  • Light emitting diodes
  • Emit light when current flows through them in the forward direction
  • Don’t have a filament that can burn out
25
Q

LDR

A
  • Light-dependant resistor
  • As light increases, the resistance decreases
  • As light decreases, the resistance increases
26
Q

Thermistor

A
  • A temperature-dependant resistor
  • As heat increases, the resistance decreases
  • As heat decreases, the resistance increases
27
Q

Layout in a series circuit

A

All the components are connected in a line

28
Q

Characteristics of a series circuit

A
  • Cannot control which components current flows through
  • Removing or disconnecting one component will break the circuit
  • Only a few things are connected in series(e.g fairy lights)
  • The same current flows through all parts of the circuit
  • Size of the current is determined by the total voltage of the cells, and the total resistance of the circuit
  • The total resistance depends on the number of components and the type of components used
29
Q

Layout in a parallel circuit

A

Each component is separately connected to the +VE and -VE of the supply

30
Q

Characteristics of a parallel circuit

A

-Removing or disconnecting one of the components will hardly affect the others

31
Q

How is charge carried in a solid metal conductors?

A

By negatively charged electrons

32
Q

Formula for charge

A

Q = I*t

33
Q

Definition of a volt

A

One volt is one joule per coulomb

34
Q

How does static build up?

A
  • Two insulating materials are rubbed together
  • The electron are scrapped off one and dumped onto the other
  • This results in opposite electrostatic charges
  • Electrically charged objects attract small objects placed near them
35
Q

How can negative charge be discharged safely?

A

By connecting the charged conductor to the earth with a metal strap: The electrons flow down the strap if the charge is negative, and flow from the ground if the charge is positive

36
Q

How are sparks caused by static electricity?

A

The greater the charge on an isolated object, the greater the voltage between the object and the earth: When the voltage gets great enough, a spark is created which jumps across the gap

Simon became inarticulate in his effort to express physics' essential illness. (7 decks)

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