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Science :D > Chapter 13: Electrical Systems > Flashcards

Chapter 13: Electrical Systems Flashcards

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1
Q

Define electricity.

A

It is the flow of electrons around a circuit, from negative to positive

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2
Q

What does a battery provide?

A

It provides the energy to push the electrons in the wire to flow.

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3
Q

What is current?

A

It is the rate of flow of electrons

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4
Q

What is a circuit?

A

It is the path that the current flows

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5
Q

What does having a high current in a circuit mean?

A

Electrons move quickly, thus there will be a brighter bulb.

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5
Q

What does having a low current in a circuit mean?

A

Electrons move slowly, thus there will be a dimmer bulb.

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5
Q

What is current flow?

A

Positive to negative

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5
Q

What is the SI unit for current?

A

Ampere (A)

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5
Q

What is electron flow?

A

Negative to positive

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6
Q

What is meant by the term ‘cancel out’?

A

Batteries connected with the same ends will cancel out

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7
Q

What does an ammeter do and how is it connected in a circuit?

A

Ammeter measures current and it is connected in series.

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8
Q

Describe the current in a parallel circuit.

A

Total current is the sum of each branching in parallel as the current divides at each junction.

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8
Q

Describe the current in a series circuit.

A

Total current stays same throughout circuit as rate of electron flow is same as there is only one pathway for current to flow.

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9
Q

Why cant the ammeter be connected in parallel?

A

The total current divides into two parts because there are different pathways. Larger current goes towards ammeter because it has low resistance. This results in a short circuit and the ammeter will fuse.

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10
Q

Should an ammeter be placed before or after the bulb?

A

Series: Doesn’t matter because current is same throughout.

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11
Q

What is potential difference across any two points?

A

It is the amount of energy needed to move one unit charge of electricity from one point to another.

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12
Q

What is the SI unit for potential difference?

A

Volts (V)

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13
Q

What is a voltmeter for and how is it connected?

A

It is to measure potential difference and is connected in parallel.

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14
Q

Describe how to calculate the potential difference in a series circuit.

A

It is the sum of the total potential difference in the circuit.

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15
Q

Describe the potential difference in a parallel circuit.

A

The total potential difference is the same.

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16
Q

What does resistance do in a circuit?

A

It opposes the flow of electrons.

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17
Q

What is resistance?

A

It is the ratio of the potential difference across it to the current flowing through the load.

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18
Q

What is the SI unit of resistance?

A

Ohm (omega sign)

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19
Q

What factors does the resistance of an object depend on?

A

Length, type of material, cross-sectional area

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20
Q

What is the relationship between the resistance of an object and its length?

A

The longer the object, the higher the resistance, the lower the current.

21
Q

What does a rheostat do?

A

It allows us to adjust the resistance in a circuit.

22
Q

What can a rheostat be used for?

A

In radios to adjust the volume and to adjust the brightness of a light bulb.

23
Q

What is the relationship between the length and resistance in a rheostat?

A

Length increases, more resistance
Length decreases, less resistance

24
Q

What is power?

A

How much electrical energy is being converted to other forms of energy per second by the electrical appliance.

25
Q

What is the SI unit for power?

A

Watts (W)

26
Q

What are the 3 hazards of electrical appliances we should look out for?

A

Damaged insulation, overloading and damp conditions

26
Q

What does the power rating of an appliance tell you?

A

It tells us how quickly an appliance converts electrical energy to other forms of energy.

27
Q

When does overloading occur?

A

When many appliances are plugged into one power outlet at the same time.

28
Q

What does the rubber insulator of wires do?

A

It protects us from direct contact with the metal wires.

29
Q

What happens when the wire’s insulation is damaged?

A

The wire becomes bare.

30
Q

Why shouldn’t you touch bare wires under damp conditions?

A

Electric current may flow through the person, causing them to get electrically shocked.

31
Q

What are the dangers of overloading?

A

Large current will flow through the wires and overheat them, which may cause an electrical fire.

32
Q

What should you do if there is an electrical fire?

A

Use a Class C fire extinguisher to put out the fire.

33
Q

What are the 3 wires found in a 3 pin plug?

A

Live wire, neutral wire and earth wire.

34
Q

What are the colors of the 3 wires found in the 3 pin plug?

A

Live wire: Brown
Earth Wire: Green and yellow
Neutral Wire: Blue

35
Q

What does the live wire do?

A

It delivers the current to the electrical appliance from the main supply.

36
Q

What does the earth wire do?

A

It connects the metal casing of the appliance to the ground. It is a precaution if the appliance is faulty.

37
Q

What does the neutral wire do?

A

It delivers back the current to the main supply to complete the circuit.

38
Q

What are the characteristics of an earth wire?

A

No current flows through it, it has a low resistance.

38
Q

What are the 5 safety features found in all household electrical circuits to deal with large currents?

A
  1. Switches
  2. Earth wire
  3. Circuit breaker
  4. Fuse
  5. Double insulation.
39
Q

What will happen in a damaged kettle?

A

In the damaged kettle, the wire with high potential is disconnected from the heating coil and touches the metal casing.

The electric potential of the casing increases to ___V.

There is a large potential difference between the ground and the kettle.

Hence, if a person touches the metal casing, the current flows through his body into the ground.

40
Q

What does a switch do?

A

It breaks or completes the electrical circuit.

41
Q

Where is a switch fitted on?

A

It is fitted onto the live wire.

42
Q

Why is the switch fitted onto the live wire?

A

So that when the appliance is switched off, it disconnects the high voltage from an appliance

43
Q

How does the fuse help in a household electrical system?

A

It makes use of the heating effect of an electric current to switch off the large current.

44
Q

What is a fuse?

A

It is a short and thin wire placed within an insulating capsule and comes in different ratings.

45
Q

Where is the fuse connected to?

A

The live wire

46
Q

What does the fuse prevent?

A

It prevents excessive high current flowing and overheating of the appliance.

46
Q

What will happen if a large current passes through the circuit?

A

It will melt, causing the circuit to be broken. This means that the fuse has been blown.

46
Q

What will happen if the live wire touches the neutral wire?

A

Too much current flowing through, short circuit occurs. This causes overheating and will cause an electrical fire.

47
Q

Will current flow if the live wire is connected to the earth wire?

A

Yes, since there is a potential difference, current will flow.

47
Q

What is a circuit breaker?

A

A safety device that automatically switches off/ trips the electrical supply when there is an excessive flow of current.

48
Q

Does the circuit breaker need to be replaced?

A

No

49
Q

What can cause a circuit breaker to trip?

A

A short circuit

50
Q

When will a short circuit in a circuit breaker happen?

A

When the current flows through a low resistance path rather than its usual path. Too much current flowing through.

51
Q

What is a double insulation a substitute for?

A

Earth wire

52
Q

Which kind of plugs is it usually found in?

A

2 pin plug

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