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Physics (useful) > Electricity ⚡︎ > Flashcards

Electricity ⚡︎ Flashcards

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1
Q

If a bulb in series melts why does series bulb 2 get brighter and parallel bulb get dimmer ?

A

Circuit resistance increases so the current decreases meaning greater share of voltage across series bulb 2

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2
Q

Energy equation

A

E = Vit

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3
Q

Why do bulbs have same light intensity but different power

A

Power is lost as thermal energy and more energy can be wasted in certain lamps

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4
Q

Ohmic conductor

A

I is directly proportional to V

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5
Q

Electricity required practical

A

Hhh

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6
Q

Principal property of a superconductor

A

Zero resistivity

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7
Q

Critical temperature

A

Material becomes superconducting at crit temperature

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8
Q

Use of a superconductor

A

Maglev trains
Magnets
Bullet trains
Particle accelerators

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9
Q

Conditions of superconductivity

A

Zero resistance
Resistance decreases with temp
Superconducts when crit temp is reached

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10
Q

Filament current alternation

A

Resistance of filament increases
As temp of filament increases

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11
Q

Explain change if a lamp is connected to a similar lamp in series

A

Voltage of supply now shared by lamps
Current is reduced

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12
Q

Explain the change if a lamp is connected to a similar lamp in parallel

A

Current through the lamp is unchanged
Both directly connected to the supply

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13
Q

Why is a filament lamp more likely to fail to switch on

A

Resistance of lamps lowered when switched on
Hence initial current will be larger
Sudden rapid change in temp

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14
Q

Electric current

A

Rate of flow of charge
I = Q/T

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15
Q

Potential difference

A

Work done per unit charge
V = W / Q

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16
Q

Resistance

A

Measure of how difficult it is for charge carriers to pass through a component
R = V / I

17
Q

Diode

A

HIGH resistance
Only small amount of current can flow

18
Q

Filament

A

Wire that heats up as current increases
Low current = no heat = Ohm’s law obeyed
If current increases then resistance increases

19
Q

Resistivity

A

How easily a material conducts electricity
p = RA/L

20
Q

Why if temp increases does the resistance increase

A

Atoms will gain kinetic energy and move more causing charge carriers to collide with the atoms more frequently so they slow down
Therefore current decreases and resistance increases (R = V / I)

21
Q

Thermistor

A

Temp increase = resistance decrease
Increase of temp causes electrons to be emitted from atoms
Therefore number of charge carriers increases and so resistance decreases

22
Q

Application of a thermistor

A

Temperature sensor

23
Q

Series equation

A

RT= R1 + R2 + R3…

24
Q

Parallel equation

A

1/RT = 1/R1 + 1/R2 + 1/R3 + …

25
Q

Power

A

Energy transferred over time
P = E / t

26
Q

Series circuit

A

Current is the same EVERYWHERE
PD is SHARED across all elements so the total sum of voltages is equal to supply PD

27
Q

Parallel circuit

A

Sum of currents in each parallel set of branches is equal to TOTAL current
PD across each branch is the same

28
Q

Series voltage

A

VT = V1 + V2 + V3 …

29
Q

Parallel voltage

A

VT = V1 = V2 = V3 …

30
Q

Kirchhoff first law

A

Total current flowing into a junction is equal to current flowing out
No charge is lost at any point

31
Q

Kirchoffs second law

A

Sum of all voltages in a series circuit is equal to the battery voltage
No energy is lost at any point

32
Q

Potential divider

A

Circuit with several resistors in series connected across a voltage source used to produce a required fraction of the source potential difference which remains constant

33
Q

LDR

A

resistance decreases as light intensity increases

34
Q

Internal resistance

A

Caused by electrons colliding with atoms inside the battery therefore some energy is lost before electrons leave the battery

35
Q

EMF

A

Energy transferred by a cell per coulomb of charge that passes through it
3 = E / Q

36
Q

Equation for power dissipation

A

P = V^2/R

Physics (useful) (11 decks)

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