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A Level Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

What is the Symbol and Units of Charge?

A

Symbol: Q
Units: Coulombs (C)

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2
Q

What is the Charge of an Electron?

A

-1.6x10^-19 C

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3
Q

What is the definition of Current?

A

Rate of change of Charge
Or
The amount of charge flowing in one second

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4
Q

What is the Symbol and Units of Current?

A

Symbol: I
Units: Ampere (A which is Cs^-1)

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5
Q

What is Potential Difference?

A

The work done per coulomb of charge

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6
Q

What is the definition of Current as an equation?

A 
Current = Charge/Time
I = ΔQ/Δt
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7
Q

What is the Symbol and Units of Potential Difference?

A

Symbol: V
Units: Volts (V which is JC^-1)

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8
Q

What is the defintion of Potential Difference as an equation?

A

Potential Difference = Work Done/Charge

V = w/Q

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9
Q

What is an alternative name of Potential Difference?

A

Voltage

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10
Q

What is the definition of Resistance?

A

The ratio of p.d to current

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11
Q

What is the Symbol and Units of Ressistance?

A

Symbol: R
Units: Omhs (Ω which is VA^-1

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12
Q

How do you calculate the number of Electrons required to make a Charge?

A

Number of Electrons = Charge/Electron Charge

n = Q/e (n = 1.6x10^-19)

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13
Q

What equation links Power, Energy and Time?

A 
Power = Energy/Time
P = E/t
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14
Q

What equation is used to convert between kWh and J?

A 
Joules = Kilowatt x Number of Seconds in a Hour
J = kWa x 3600
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15
Q

What set of equations link Power, Potential Difference, Current and Ressistance?

A 
Power = p.d x Current = Current² x Ressistance = p.d²/Ressistance
P = VI = I²R = V²/R
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16
Q

What is an Ohmic Conductor?

A

A conductor where the p.d across it directly proportional to the current

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17
Q

What is the Operating Voltage of a Diode?

A

The p.d which the diode occupies

generaly about 7V

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18
Q

What happens to most Conductors when the temperature increases?

A

The resistance increases

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19
Q

Why does Resiatance increase with temperature?

A

Increased lattice vibration due to more energy
∴ elctrons find it harder to flow
∴ resistance increases

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20
Q

What is Superconductor?

A

A material that when at or beneath the resistance becomes Zero
(Not just close to Zero, But is Zero)

21
Q

What is a use of Superconductors?

A

MRI scanners

conductors when a very large magnetic field is needed

22
Q

What is a Semiconductor?

A

A materials whose resistance decreases as temperature increases

23
Q

How does a Semiconductor work?

A

The temperature increase causes an increase in “free” electrons
∴ more charge is available
∴ resistance decreases

24
Q

What is a Thermistor?

A

An electrical component that is based on semiconductors

Temp↑ cause Resistance↓

25
Q

How is Current spread out in a Series Circuit?

A

Current is the same at all points within the circuit

26
Q

How is p.d spread out in a Series Circuit?

A

It is the product of the current and the resistance of that component.

27
Q

How is the total p.d of a Series Circuit calculated

A

V(total) = ΣV(components)

28
Q

How is the total Resistance of a Series Circuit calculated?

A

R(total) = ΣR(compoents)

29
Q

What is the Potential Divider equation?

A

V(1) / V(total) = R(1) / R(total)

30
Q

How is the Current spread out in a Parallel Circuit?

A

Current in each branch is based of its resistance

31
Q

How is the total Current in a Parallel Circuit calculated?

A

I(total) = Σ I (of each branch)

32
Q

How is the total Resistance clalculated within a Parallel Circuit?

A

1/R(total) = 1/ΣR(of each branch)

33
Q

How is p.d spread out within a Parallel Circuit?

A

p.d is the same across every branch of the circuit

34
Q

What is a quick way of calculating the total Resistance of identical resistors in parallel?

A

Total Resistance = Resistance / Number of Resistors

R(total) = R/n

35
Q

What is the Symbol and Units of Resistivity?

A

Symbol: ρ
Units: Ωm

36
Q

What is the equation of Resistivity?

A 
Resistivity = Resistance x Cross-Sectional Area / Length
ρ = RA/L
37
Q

What is the Symbol and Units of Electromotive Force?

A

Symbol: ε
Units: V

38
Q

Define E.M.F?

A

The p.d of a supply when no current is being drawn

39
Q

What is the Symbol and Units of Internal Resistance?

A

Symbol: r
Units: Ω

40
Q

What is Internal Resistance?

A

The resistance of a power supply

41
Q

What is Load?

A

AKA External Resistance

The resistance outside of a power supply

42
Q

What is the equation of E.M.F?

A

E.M.F = Current (Internal resistance + external resistance)
ε = I x (R+r)
Or
E.M.F = p.d across load + (Current x Internal Resistance)
ε = V+Ir

43
Q

What happens if a circuit has a small load?

A

A large curent will be drawn
The p.d lost on intenal resistance will be large
p.d supplied to load will be a lot less than the E.M.F

44
Q

What is Kirchoff’s First Law?

A

The sum of the currents at a point is equal to Zero
Or
Total current in is equal to total current out

45
Q

What is Kirchoff’s Second Law?

A

The sum of the E.M.F is equal to the sum of the p.d around a closed loop
Or
The total E.M.F provided is equal to the p.d across the components within a closed loop

46
Q

What is a Rheostat?

A

A resistor where resistance is mechanically changed, by moving the point of contact allong it.
It is made of a long coil of wire

47
Q

What is an LDR?

A

A resistor where resistance is based of light intensity.

Light Intensity↑ cause Tesistance↓

48
Q

What is a potential divider circuit?

A

a simple circuit that uses resisters(or thermistors,rheostats or LDR’s) to supply a variable potential difference

49
Q

What does a potential divider circuit look like?

A

Look in work book

A Level Physics (16 decks)

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