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GCSE Physics [AQA] > P2 - Electricity > Flashcards

P2 - Electricity Flashcards

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1
Q

What is the charge of electrons? How does this affect movement in a circuit?

A

. Negative
. Electrons are repelled by the negative end of the cell

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2
Q

What is current?

A

The flow of electrical charge.

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3
Q

What is current measured in? using which equipment?

A

Amps
Ammeter

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4
Q

What is the equation for current?

A

Charge flow (C) = current (A) x time (s)

Rearranged:
Current = charge flow ÷ time

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5
Q

What is potential difference?

A

The energy transferred, per coulomb of charge that passes, between two points in a circuit.

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6
Q

What is potential difference measured in? using which equipment?

A

Volts
Voltmeter

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7
Q

What is the equation for potential difference?

A

potential difference (v) = current (A) x resistance (Ω)

V = i x R

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8
Q

What is resistance?

A

When conductors oppose the flow of electrical current.

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9
Q

What is the equation for resistance?

A

Resistance = potential difference ÷ current

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10
Q

What is the equation for charge flow?

A

Charge flow (c) = current (A) x time (s)

Q = it

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11
Q

What is the equation for energy transferred?

A

Energy transferred (j) = charge flow (c) x potential difference (v)

Energy transferred = power x time

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12
Q

What does I-V characteristic mean?

A

A graph which shows how the current (i) flowing through a component changes as the potential difference (v) across it is increased.

Linear components have an I-V characteristic that is a straight line
Non-linear components have an I-V characteristic that is a curved line

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13
Q

What is the shape of an I-V characteristic graph for an ohmic conductor?

A

A straight line because current through an ohmic conductor (at a constant temperature) is directly proportional to potential difference.

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14
Q

What is the shape of an I-V characteristic graph for a filament lamp?

A

A curved line because…

As current increases, the temperature of the filament increases, so the resistance increases. This means less current can flow per unit pd, so the graph gets shallower.

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15
Q

What is the shape of an I-V characteristic graph for a diode?

A
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16
Q

What is a thermistor?

A

A thermistor is a temperature dependent resistor.

In hot conditions, the resistance drops.
In cold conditions, the resistance goes up.

Thermistors make useful temperature detectors, e.g. car engine temperature sensors and electronic thermostats.

17
Q

What is an LDR?

A

A light dependent resistor
= A resistor that is dependent on the intensity of light

In bright light, the resistance falls
In darkness, the resistance is highest

Used for automatic night lights, outdoor lighting, and burglar detectors.

18
Q

How are LDRs and thermistors used in sensing circuits?

A

Sensing circuits can be used to turn on or increase the power to components depending on the conditions that they are in.

19
Q

What is a series circuit?

A
20
Q

What is a parallel circuit?

A
21
Q

Investigate resistance in a series circuit

A
22
Q

Investigate resistance in a parallel circuit

A
23
Q

Your results should match the resistance rules

A
24
Q

Why is the voltmeter placed in parallel to the component?

A

Because the voltmeter measures the difference in the energy the electrons have before they go into the component and after they have left it.

25
Q

What is the difference between alternating current and direct current?

A
26
Q

What is the colour of the live wire in cables?
What is the function of the live wire in cables?

A

Brown

The live wire provides the alternating potential difference (at about 230v) from the mains supply

27
Q

What is the colour of the neutral wire in cables?
What is the function of the neutral wire in cables?

A

Blue

The neutral wire completes the circuit - when the appliance is operating normally, current flows through the live and neutral wires. It is around 0v.

28
Q

What is the colour of the earth wire in cables?
What is the function of the earth wire in cables?

A

Green and yellow

It is for protecting the wiring, and for safety - it stops the appliance casing from becoming live. It doesn’t actually carry a current - only when there’s a fault. It’s also at 0v.

29
Q

How can a live wire give you an electric shock?

A
30
Q

Energy is transferred from cells and other sources

A
31
Q

What is the national grid?

A

A network of cables and transformers across the country, that transfer electricity from power stations to consumers.

32
Q

What is the function of a step-up transformer?

A

To increase the potential difference of the electricity. This reduces the current, which means less power is lost during transmission.

33
Q

What is the function of a step-down transformer?

A

To reduce the potential difference of the electricity, which means that current increases.

34
Q

What are the advantages of using overground cables for transmitting electricity?

A

. Cheap
. No cooling or insulation required
. Easy to repair

35
Q

What are the advantages of using overground cables for transmitting electricity?

A

. Cheap
. No cooling or insulation required
. Easy to repair

36
Q

What are the advantages of using underground cables for transmitting electricity?

A

. No visual pollution
. No danger of electrocution
. Are not easily damaged

GCSE Physics [AQA] (7 decks)

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