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Physics > Electricity > Flashcards

Electricity Flashcards

1
Q

We buy electrical energy in units called

A

Kilowatt hours (kWh)

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2
Q

1kW = ? W

A

1000

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3
Q

1kW charged by Eskom =

A

R1,70

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4
Q

Paying for electricity formula

A

Cost = power x time x rate

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5
Q

Source of the electric current

A

Electrical cells

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6
Q

In a cell -

A

Chemical energy is converted into electrical energy

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7
Q

Series circuit only provides

A

One pathway for the charge to move

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8
Q

Charge:
1. Unit
2. Symbol

A
  1. Coulomb (C)
  2. Q
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9
Q

Current:
1. Unit
2. Symbol

A
  1. Amperes (A)
  2. I
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10
Q

Time:
1. Unit
2. Symbol

A
  1. Seconds (s)
  2. t
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11
Q

Resistance:
1. Unit
2. Symbol

A
  1. Ohms (Ω)
  2. R
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12
Q

Potential Difference:
1. Unit
2. Symbol

A
  1. Volts (V)
  2. Voltage (V)
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13
Q

Effects of an electric current

A
  • Heating effect
  • Magnetic effect
  • Chemical effect
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14
Q

Magnetic effect

A
  • When an electric current flows in a conducting wire, a magnetic field develops in the space around the conductor
  • Magnetic field is in the form of concentric circles around the conductor
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15
Q

Series Circuit current

A

A1 = A2 = A3

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16
Q

Parallel Circuit current

A

A1 = total current
A1 = A2 + A3

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17
Q

Current formula

A

Current = charge moved ÷ time taken
I = Q ÷ t

18
Q

When a cell is in a complete circuit …

A

The chemicals (chemical energy) react with each other

19
Q

The charge are given _________ energy they need to ______

A

Potential
Start moving through the circuit

20
Q

When a charge receives more energy

A

It releases more energy

21
Q

Why is a voltmeter connected in parallel?

A

Because it measures potential difference across the ends of a cell/resistor (light bulb)

22
Q

Why is an ammeter connected in series?

A

So that all the current flows through the ammeter and can be measured

23
Q

Voltmeter connected in ….

24
Q

Ammeter connected in ….

25
Q

Voltmeter has ________ resistance because

A

Very high
It forces current to flow through the cell/lightbulb not through the voltmeter

26
Q

Ammeter has _______ resistance because

A

Low
It allows the current to flow through the ammeter so that it can measure it

27
Q

Work done =

A

Energy transferred

28
Q

1 Volt =

A

1 J per Coulomb

29
Q

Ohmic Resistor

A
  • The graph for V against I is a straight line that goes through the origin
  • Relationship between current and potential difference is directly proportional
30
Q

Non-Ohmic resistor

A
  • The graph for V against I is not a straight line
31
Q

Resistance formula

A

Resistance = potential difference ÷current
R = V ÷ I

32
Q

State Ohm’s Law

A

Current through a conductor is directly proportional to the potential difference across the conductor at constant temperature

33
Q

Factors that affect resistance

A
  • Type of material
  • Length of conductor
  • Thickness of conductor
  • Temperature of material
34
Q

Type of metal used

A

Different conducting materials have different resistances

35
Q

Length of conductor

A
  • More length = more resistance
  • Less length = less resistance
  • Resistance is directly proportional to the length of metal conductor
36
Q

Thickness of conductor

A
  • Thinner conductor = more resistance
  • Thicker conductor = less resistance
  • Resistance is inversely proportional to the thickness of metal conductor
  • Inversely proportional graph = hyperbola
37
Q

Temperature of conductor

A
  • Hotter conductors = more resistance
  • Cooler conductors = less resistance
38
Q

Potential Difference in Series

A

The sum of potential difference across each individual resistor is equal to the potential difference across the battery

39
Q

Potential Difference in Parallel

A

The potential difference across each resistor in parallel is equal to each other and equal to the potential difference across the battery

40
Q

Resistors in series are called

A

Potential dividers

41
Q

Resistors in parallel are called

A

Current dividers

42
Q

Kilowatt hour is another

A

Unit for energy

Physics (7 decks)

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