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Science > Current Electricity - Gr.9 > Flashcards

Current Electricity - Gr.9 Flashcards

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1
Q

Electrical Power

What is electrical power, its symbol and unit?

A

Electrical power is the rate of change of elctrical energy. Its symbol is P and unit is joules (J)/ Watt (W).

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2
Q

Electrical Power

How do you turn 100w to Kh?

A

Divide by 1000 (0.1)

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3
Q

Calculate the Efficiency:
A lightblub uses 103J and produces 40J.

(output/input)100

A

(40/103)100
0.388(100)
38.8

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4
Q

Calculate cost of Electricity:
75W
Electricity costs 9.5 cents/kWh
how much would it cost for 1 year for 4 hr/day.

A
  1. 75/1000=0.075kW
  2. 4(365)= 1460h
  3. 1460x0.075x9.5=1040 cents
  4. 1040/100= $10.40
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5
Q

Types of Energy

What is:
Kinetic Energy
Chemical Energy
Nuclear Energy

All forms of energy can be converted into other forms

A
  1. The energy of motion
  2. engory stored in the bonds of atoms and molecules
  3. energy stored in the nucleas of an atom
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6
Q

What are renewable/non-renewable sources?

A

Renewable energy sources can be replaced or restocked within humanlife.
Non-renewable cannot be replaced or restocked within human life.

Eg. water and wind. fossil feuls and Uranium

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7
Q

What are the three factors to consider when assseing an energy source?

A
  1. Impact on eco-systems
  2. Impact on society
  3. Economic-consideration (Technology available, efficent, cost-effictive etc.)
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8
Q

What is a:
Curcuit breaker (rainbow)
Variable resistor (rheostat) (arrow going through a resistor)
Ground connection (down arrow)

A
  1. Like fuse, but can be reset.
  2. A resistor but controlable
  3. connects to the ground to allow discharge.
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9
Q

Curcuit boards

When electrons finish going through a lightbulb, do they have to return back to the battery?

A
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10
Q

Curcuit boards

If a switch is open, can electrons flow?

A

No.
There must be a close curcuit (complete path) for electrons to travel.

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11
Q

Curcuit boards

What is an open curcuit?

A

When there is a break/incomplete path in the circuit.

Ex. open switch blocks the path for electrons

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12
Q

Circuit boards

What does a complete/controlled electrical circuit have?

A
  1. Energy source
  2. Load
  3. connecting wires
  4. Switch
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13
Q

Electrical circuits

What is a short Circuit?

A

A circuit that has a path that lets electrons flow, but no load.

It is very dangerous

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14
Q

What is Current?

A

The flow of electrons

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15
Q

Electrical circuits

What is a
Dry Cell
Wet Cell
Primary Cell
Secondary Cell
Fuel Cell
Solar

A
  1. Contains Paste electrolyte
  2. Contains Liquid electrolyte
  3. Cannot be recharged
  4. Can be recharged
  5. Converts chemical reactions of feul to energy
  6. Converts Sunlight to energy
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16
Q

Electrical circuits

Electrons travel in big groups called a _____.

A

Coulomb

17
Q

Electrical circuits

What is Electric Current, symbol and unit of measurement?

A

Measures the rate at which electrons are flowing in a circuit.
I and Ampheres (A)

18
Q

Electrical circuits

What device can be used to measure current?

A

Ammeter.

19
Q

What is the symbol/unit for Current, Charge and Time?

A
  1. I and amperes (A)
  2. Q and Coulomb (c)
  3. t and seconds (s)
20
Q

If 240c of charge passes a point in a circuit in 300s what is the current through that point in the circuit?

Q/t=I

A

240/300=0.8A

21
Q

What is Electrical Resistance?

A

A property of a substance that hinders/resists electric current and convertys electrical energy to other forms of energy.

Like a speedbimp

22
Q

What is a resistor?

A

A resistor is a device used to decrease the current.

The higher the resistance, the slower the current.

23
Q

What is the symbol and unit of measurement for resistance?

A

(R)=Ohms (Ω)

24
Q

A technician measured the current as 4.7A.The total potential difference is 12V. What is the resistance?
Ohms Law: R=V/I

A
  1. 12/4.7A
  2. R=25.53 Ω
  3. R=26Ω
25
Q

What are the factors affecting the resistance of wires?

A
  • The type of material (some have less resistance than others)
  • The length (shorter wires are faster)
  • The thickness (thicker wires are faster)
  • Temperature (cold has less resistance than hot.)
26
Q

How is the Current in a series circuit? Parallel?

A

In a series, the current is the same all throughout different points.
In a parallel, the total current at the source is the sum of all the current.

27
Q

How is the potential difference in a series circuit? Parallel?

A

In a series, the potential difference at the load is the total sum of the potential difference of all voltage.
In a parallel, the voltage at the source is the same all throughout different points.

28
Q

How is the resistance in a series circuit?

A

In a series, the resistance at the source is the total sum of all the resistance.

29
Q

Electrical energy

How do you change from W to kW?

A

Divide by 1000 (ex. 250W= 0.25kW).

30
Q

What is electrical energy?

A

Electrical energy is the rate of energy be passed though. its energy used for powering things.

31
Q

What are two differences and similarities between a parallel and a series circuit?

A
  1. They both need a load, wires and source
  2. voltmeters still have to be connected in parallel.

1.one circuit has only one path
2.current is equal all throughout in a series circuit.

32
Q

What happens to a lightbulb when more and more are added in series?

A

The more loads there are, the dimmer each bulb will be. It is because the voltage has to be spread accross more loads.

33
Q

Explain a method of generating electricity. Name an advantage and disadvantage.

A
  • Wind energy. It is when wind spins a turbine which causes teh turbine to spin the electric generator creating wind energy.
  • Wind energy is renewable
  • Too loud and ruins scenery
34
Q

How would decreasing the diameter of a conductor affect its resistance?

A

It will increase resistance because the thinner a wire is, the less space for electrons to travel.

35
Q

How would extending the length of a conductor affect its resistance?

A

It will increase in resistance because the longer the cord, the more resistance electrons will travel through and more energy will be lost.

36
Q

How will switching from silver to copper wire affect its resistance.

A

The type of material can impact the resistance. Since copper is a better conductor, the resistance will decrease.

Science (4 decks)

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