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Physics ATAR U1 > Electricity > Flashcards

Electricity Flashcards

(51 cards)

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1
Q

What is charge

A

Where particles have positive / negative / neutral charge

Like charges repel, opposite charges attract

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2
Q

What are electric forces

A

Non-contact

Vector quantity (Has magnitude and direction)

Strength of force depends on distance between charges
- Greater unbalanced charge = Greater force

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3
Q

What are electrical conductors

A

Electrons free to move, charge can flow easily

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4
Q

What are electrical insulators

A

Electrons can’t move, charge can’t flow

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5
Q

What are electrical semi-conductors

A

Conducts electricity under certain circumstances

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6
Q

What is current

A

The flow of electric charge, net amount of charge passing certain point in given time interval

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7
Q

What do you need for current

A

An electric field, supply energy to move charges

Charges being free to move

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8
Q

How to measure current in circuits

A

Current is conserved quantity, charge carriers always somewhere

Current that flows in = Current that flows out

Measured using ammeter, connected anywhere

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9
Q

What is formula for current

A

Current (A) = Charge (C) / Time (s)

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10
Q

What is Direct-Current (DC)

A

Net charge flows in 1 direction, power from batteries

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11
Q

What is Alternating-Current (AC)

A

Charge flow alternates, moves back and forth, power from wall socket

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12
Q

What is electric potential

A

Potential energy per unit of charge (Coulomb)

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13
Q

What is potential energy

A

“Stored” energy with capacity to do work
- Gravitational Potential Energy
- Elastic Potential Energy
- Electric Potential Energy

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14
Q

What is potential difference / voltage

A

Change in potential energy per unit charge between two defined points in circuit

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15
Q

Why do electrons require energy to move

A

Charged particles naturally move from high to low potential

Requires energy to move from low to high potential = Electrons require energy to move

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16
Q

What is 1 volt

A

1 J/ Coulomb

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17
Q

How do you measure potential difference using voltmeter

A

Measured by comparing two different locations on circuit

Exists if charged particles gain/lose potential energy

Measured using voltmeter

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18
Q

What is formula for potential difference

A

Voltage = Change in Potential Energy / Work (J) / Electric Charge (C)

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19
Q

How do you create a current

A

Potential difference applied to conductor

  • Creates electric field
  • Exorts force on electric charges
  • Electric charges move = Current
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20
Q

What is power

A

Rate of energy transfer

Power usage of element determined from voltage & current of element

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21
Q

What are the formulas of power

Study These Flashcards
A

Power = Work Done (J) / Time (s)

Power = Voltage (V) * Current (A)

22
Q

What is a circuit

Study These Flashcards
A

Path through where electricity flows

23
Q

What are the requirements for a circuit

Study These Flashcards
A

Power source, produces EMF

Complete path of conducting material

24
Q

What is a series circuit

Study These Flashcards
A

All elements arranged in chain, only one path for current

25
What is the resistance in a series circuit
Total Resistance = Sum of individual resistances Rt = R1 + R2 + R3 + ...
26
What is voltage in a series circuit
Total Voltage = Sum of individual voltages Vt = V1 + V2 + V3 + ...
27
What is current in a series circuit
Current is the same in every part of circuit Current in = Current out
28
What is a parallel circuit
Each component directly connected to power source Atleast two pathways for current to travel
29
What is the resistance in a parallel circuit
Total Resistance = Amount of resistance a 'single' resistor needs to equal overall effect 1 / Rt = (1/R1) + (1/R2) + (1/R3) + ...
30
What is the voltage in a parallel circuit
Same voltage applied to each pathway of circuit
31
What is the current in a parallel circuit
Current in = Current out Current split between each branch Split equally if resistance of each branch is the same
32
What is electrical resistance
Measure of how hard it is for current to flow through material
33
How does resistance work in wires
Charge moves through wire in zig-zags, as it collides with atoms In collisions, charges transfer some energy to atoms = Being resisted
34
How does resistivity affect resistance
How much a material opposes flow of charge Some materials resist movement of charge more than others
35
How does temperature affect resistance
Increase in temperature = Increase in resistance Atoms vibrate faster, charge through conductor has more collisions
36
How does length of wire affect resistance
Longer wire = Higher resistance Charges experience more collisions before reaching end of wire
37
How does area of wire affect resistance
Higher area = Lower resistance More area for charges to move = Less collisions
38
What is Ohm's Law
Current flowing through substance directly proportional to voltage Resistance affects current & voltage
39
What is the formula for resistance
Resistance (Ohms) = Voltage (V) / Current (A)
40
What are ohmic devices
Resistance constant for wide range of voltages & currents Obeys Ohm's Law Most wires & resistors
41
What are non-ohmic devices
Resistance not constant, varies depending on current & voltage Doesn't obey Ohm's Law Light diodes, digital devices
42
What are thermal hazards
Excessive electric power, undesired thermal effect Eg. Starting a fire in the wall of a house
43
What are short circuits
Low resistance path between positive & negative terminals of voltage source - Resistance small, power large = Melt / Cause Fire
44
What are shock hazards
Current passes through body (Severely painful to lethal) - Voltage related to flow, energy available for flow Amount of current depends on bodies resistance - Dry skin = High resistance (Good) - Wet skin = Low resistance, can be lethal (Bad)
45
What are electric shock fatalities
Current puts heart into fibrillation (Irregular heartbeat) Effect of shock depends on: - Amount of current - Path of current - Duration of shock - Frequency of current
46
How do you prevent electrical shocks)
Unplug appliances when working on / cleaning them Keep appliances dry, use dry hands Qualified professionals do maintenance Touch something 'live' with back of hand, if muscles contract, will pull away from object instead of grabbing it
47
What is a fuse and circuit breaker, and what is the difference
Wire overload Innner wires overheat & melt when current too high (Breaks circuit) Limits excessive currents Works for small voltages / currents (Eg. Household) Won't save from electrocution Circuit breakers can be reset, fuses need to be replaced
48
What are the types of wires in a household
Active Wire: Carries current from power station Neutral Wire: Closes circuit so current can flow Earth Wire: Safety device, connected to conductive parts of appliances
49
What does an earth wire do
If active wire in metal case touches the metal casing, whole case becomes electrically live To prevent this, a short circuit is created by earth wire, current immediately flows to the Earth
50
What is double insulation
Device never exposes operator to active wire even if it becomes disconnected / loose - Done by ensuring outer casing insulated from inner workings - Earth wire not needed
51
What are residual current devices (RCDs)
Cuts the circuit when Active Current != Neutral Current - Should be the same as current in = current out - If not same, leakage of current (Eg. To Earth or To Person) Cuts at as little different as 30mA

Physics ATAR U1 (6 decks)

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