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Physics IGCSE > Electricity > Flashcards

Electricity Flashcards

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1
Q 
current : ?
charge : ?
resistance : ?
time : ?
potential difference : ?
power : ?
A 
current : Ampere (A)
charge : coulomb (C)
resistance : ohm (Ω)
time : second (s)
potential difference : volt (V)
power : watt (W)
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2
Q

How does insulation protect the device or user in a domestic appliance?

A

All insulation is is covering a live wire (a wire that is conducting electricity) with a material that is not an electrical conductor. This means the wire is safe to touch as the current is contained within the wiring as it can’t pass through the layer of insulation.

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3
Q

How does double insulation protect the device or user in a domestic appliance?

A

Some appliances, for example vacuum cleaners and electric drills, do not have an earth wire. This is because they have plastic casings, or they have been designed so that the live wire cannot touch the casing. As a result, the casing cannot give an electric shock, even if the wires inside becomes loose and touched the casing.

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4
Q

How does earthing protect the device or user in a domestic appliance?

A

Many electrical appliances, for example cookers, washing machines and fridges have metal cases. The earth wire creates a safe route for the current to flow through if the live wire touches the metal casing (otherwise the current would flow through the case and it is likely you would get an electric shock).

However, the earth wire is connected to the metal casing so that the current goes through the earth wire instead of causing an electric shock. A strong current surges through the earth wire because it has a very low resistance. This breaks the fuse and disconnects the appliance.

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5
Q

How do fuses protect the device or user in a domestic appliance?

A

If a fault in the circuit causes too much current to flow, the fuse breaks the circuit. The fuse contains a piece of wire which melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.

Fuses in plugs are made in standard ratings. The most common are 3 A, 5 A and 13 A. The fuse should be rated at a slightly higher current than the device needs. Foe example, if the device works at 3 A, use a 5 A fuse, if the device works at 10 A, use a 13 A fuse.

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6
Q

How do circuit breakers protect the device or user in a domestic appliance?

A

Circuit breakers contain an electromagnet that activates if the current goes above a certain limit (different limits for different appliances). Should the current go above the limit of an appliance, the electromagnet pulls an iron switch towards it, this opens the switch, consequently breaking the circuit.

Residual current circuit breakers (RCCBs) protect some circuits. They detect a difference in the current between the live and neutral wires. RCCBs work much faster than fuses do. (For exams, you do not need to know how they work, just what they do)

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7
Q

Why does a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts?

A

As the resistor slows down the electrons, the kinetic energy that was moving them is transferred into heat energy. This can be used in hairdryers.

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8
Q

What is the relationship between power, current and voltage?

A

power (w) = current (A) x voltage (V)

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9
Q

How do you select the appropriate fuse for a curcuit?

A

when looking at a circuit a component will be given a power and a voltage appropriate to run at then the current can be calculated so the rating of the fuse can be selected for slightly higher than that.

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10
Q

What is the relationship between energy transferred, current, voltage and time?

A

Energy (J) = potential difference (V) x current (A) x Time (s)

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11
Q

What is AC?

A

AC (alternating current) is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.

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12
Q

What is DC?

A

DC (direct current) is constant. And is produced from a battery and used in some sensitive components like in computing.

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13
Q

What is DC?

A

DC (direct current) is constant. And is produced from a battery and used in some sensitive components like in computing.

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14
Q

What is the difference between AC and DC?

A

AC is mains electricity and DC is supplied by batteries. Batteries/Cell

DC (batteries/cells):

  • Current flows only in one direction.
  • Voltage is low (1.5V for standard batteries)
  • Amount of current decreases as battery will run out.

AC (Main electricity):

  • Constantly changes direction.
  • High voltage (230V)
  • Amount of current stays constant.
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15
Q

Advantages of parallel circuits

A
  • Components (e.g. bulbs) may be switched on/off independently.
  • If one component breaks, current can still flow through the other parts of the circuit.
  • Bulbs maintain a similar brightness.
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16
Q

Advantages of series circuits

A
  • Fewer wires, cheaper and easier to assemble.

- Uses less power

17
Q

What is current?

A

The rate of flow of charge so I=Q/t

18
Q

What is the voltage?

A

The voltage is the what pushes the electrons around.

19
Q

What is the voltage?

A

The voltage is the what pushes the electrons around.

20
Q

What happens to the current when voltage increases?

A

If voltage is increased, current increase.
Electrons are “pushed” harder and ∴ flow “faster”
(only if EVERYTHING in circuit is CONSTANT)

21
Q

State a way you could increase current?

A

Adding more batteries ∴ increasing voltage, ∴ increasing current.

22
Q

The more components in a circuit, the lower the…

A

Current

23
Q

How do you increase resistance and decrease current?

A

achieved by adding more components. Since V = IR

24
Q

How do you decrease resistance and increase current?

A

achieved by removing components. Since V = IR

25
Q

What can be used to indicate the presence of a current in a circuit?

A

lamps and LEDs - A lamp can be added to a circuit to check for a current. If current is flowing, the lamp will light up.

26
Q

What is the relationship between voltage, current and resistance?

A

Potential difference (V) = Current (A) x Resistance (Ω) (V=IxR)

27
Q

What is use the relationship between charge, current and time?

A

Charge (C) = Current (A) x Time (s) (Q = I × t )

28
Q

What is the flow of the electric current in solid metallic conductors like?

A

The current in solid metallic conductors is a flow of negatively charged electrons.

29
Q

What is the flow of the electric current in solid metallic conductors like?

A

The current in solid metallic conductors is a flow of negatively charged electrons.

30
Q

At a junction, what happens to the current?

A

At a junction current ‘splits’ to take both paths.
It comes back together when the paths meet again.
I1 = I2 + I3 +I4

31
Q

What is the current in the series across two components like?

A

it’s the same (IT = T1 = T2)

32
Q

What is the voltage in the series across two components like?

A

it’s shared (VT = V1 + V2)

33
Q

calculate the currents, voltages and resistances of two resistive components connected in a series circuit:

A

VT = V1 + V2

IT = I1 = I2

RT = R1 + R2

34
Q

What is voltage(V)?

A

The energy transferred (j) / charge passed (C)

35
Q

What is volt(V)?

A

joule(j) / coulomb(C)

36
Q

What is the relationship between energy transferred, charge and voltage?

A

Energy Transferred (J) = charge (C) x Voltage (V) ((E = Q × V))

37
Q

What is Q?

A

Charge, measured in coulombs (C)

38
Q

What is E?

A

Energy, measured in joules (J)

39
Q

What is V?

A

Voltage, measured in volts (v)

Physics IGCSE (9 decks)

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