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Physics - Domestic Electricity > Physics - Domestic Electricity > Flashcards

Physics - Domestic Electricity Flashcards

1
Q

What is the unit of power used in a domestic setting?

A

Kilowatts (kW)

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2
Q

Which equation calculates how many units of electrical energy are used?

A

Units used (kWh) = Power (kW) x Time (h)

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3
Q

What are the units for E (energy transferred), P (power) and t (time) in the equation E=Pt?

A

E is energy transferred in joules (J), P is power in W (W) and t is time in seconds (s)

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4
Q

Which equation is used to calculate the cost of electrical energy?

A

Cost (p) = Units used (kWh) x Cost per unit (p)

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5
Q

What is the Fuse, and what is its purpose?

A

The Fuse contains a thin wire with a low melting point - if the current is too high, the wire melts, and breaks the circuit.

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6
Q

What is the Residual Current Circuit Breaker (rccb) and what is its purpose?

A

The rccb detects when there is a difference in current between the live and neutral wires. If there is a difference, the rccb trips and will switch off the circuits. It protects the user.

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7
Q

What is the Miniature Circuit Breaker (mcb) and what is its purpose?

A

The mcb detects when too much current is drawn from the mains supply. It protects the circuit, and prevents a circuit overload, or a short-circuit.

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8
Q

Why are circuit breakers are better than fuses?

A

Circuit breakers are faster acting than fuses and can be reset.

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9
Q

What is the function of the Ring Main?

A

The Ring Main delivers electricity from the consumer unit to the sockets. Arranged in parallel circuits.

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10
Q

What are the advantages of the Ring Main?

A
  • Each circuit can be controlled separately
  • Easy to add to the ring main because each circuit gets 230V
  • The current travels in two paths so the wire can carry less current and can be made thinner
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11
Q

What is the Consumer Unit and what is its purpose?

A

The consumer unit distributes electricity from the mains supply to individual circuits within a house, and contains circuit breakers.

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12
Q

Which two cables does the 2 Core Cable contain?

A

The Live and Neutral Wire

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13
Q

Which three cables does the 3 Core Cable contain?

A

The Live, Neutral and Earth Wire

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14
Q

What is the function of the Live Wire?

A

Carries the current from the mains supply to the appliance at a high voltage

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15
Q

What is the function of the Neutral Wire?

A

Returns the current from the appliance to the mains supply at a low voltage

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16
Q

What is the function of the Earth Wire?

A

If a fault occurs and an appliance with a metal casing becomes live, the earth wire provides a safe route for the current to flow to the ground. This process is called earthing. In a normal circuit there is no current in the earth wire.

17
Q

How do you calculate percentage efficiency?

A

% efficiency = (Energy (or power) usually transferred ÷ Total energy (or power) supplied) x 100

18
Q

How do you calculate Payback Time?

A

Payback Time (years) = Cost of insulation (£) ÷ Money saved per year (£)

19
Q

What is Alternating Current?

A

Alternating current (ac) is current that constantly changes in directions and magnitude (size).

20
Q

What is Direct Current?

A

Direct current (dc) is current that has the same direction and magnitude (size).

21
Q

What is the source for Alternating Current?

A

The Mains Supply

22
Q

What is the voltage and frequency for the current that comes from the Mains Supply?

A

Voltage: 230V

Frequency: 50Hz

23
Q

What are the sources for Direct Current?

A

Batteries, Cells

24
Q

What is Double Insulation?

A

Doubly Insulated appliances are ones with protective plastic casing.

25
Q

Which wire of a 3 pin plug is brown?

A

Live Wire

26
Q

Which wire of a 3 pin plug is blue?

A

Neutral Wire

27
Q

Which wire of a 3 pin plug is yellow and green?

A

Earth Wire

Physics - Domestic Electricity (1 decks)

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