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electricity Flashcards

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1
Q

What 2 things are needed for a charge to flow?

A

~The circuit must be closed (no open switches)
~Must have a source of potential difference

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2
Q

What is current?

A

The flow of electrical charge.

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3
Q

What does Q = It stand for?

A

Charge (in coulombs) = current (in amps) x time (in seconds).

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4
Q

Current through a component depends on…

A

~The resistance of the component
~The potential difference across the component

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5
Q

What does V = IR stand for?

A

Potential difference (in volts) = current (in amps) x resistance (in ohms).

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6
Q

What is the gradients for a resistor, filament lamp or diode graph?

A

1 / resistance.

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7
Q

How does resistance change with current?

A

~When current is increased electrons have more energy
~They collide with atoms in the resistor when they flow through it
~This transfers energy to the atoms causing them to vibrate more
~Making it more difficult for electrons to flow through the resistor

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8
Q

As resistance increases…

A

Current decreases.

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9
Q

How does resistance change with temperature in normal wires?

A

Same as with current as the atoms vibrate when hot.

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10
Q

How does resistance change with temperature in a thermistor?

A

Hotter temperatures mean the resistance is lower.

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11
Q

How does resistance change with length?

A

The greater the length the more resistance and the lower the current (electrons have to go through more resistor atoms).

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12
Q

How does resistance change with light in an LDR?

A

The greater the light intensity, the lower the resistance.

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13
Q

How does resistance change with voltage in diodes?

A

Diodes allow current to flow freely in one direction but in the opposite direction, it has a very high resistance so no current can flow.

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14
Q

In series circuits, current only flows…

A

In a single path.

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15
Q

In series circuits, current is the same…

A

Everywhere.

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16
Q

In a series circuit, potential difference…

A

Is shared across the whole circuit.

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17
Q

In a series circuit, the potential difference of the power supply =

A

The sum of the potential difference across each component.

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18
Q

In parallel circuits, current…

A

Splits into multiple paths.

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19
Q

In a parallel circuit, potential difference is the same…

A

Across each branch.

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20
Q

In a parallel circuit, the potential difference of the power supply =

A

The potential difference of each branch.

21
Q

Why does the potential difference of the power supply = the potential difference of each branch in a parallel circuit?

A

Because the charge can only pass through any one branch.

22
Q

In a parallel circuit, current is shared…

A

Between each branch.

23
Q

In a parallel circuit, current through source =

A

Sum of current through each branch.

24
Q

In a parallel circuit, total resistance is less than…

A

The branch with the smallest resistance.

25
Q

What colour is the live wire?

A

Brown

26
Q

What is the potential difference of the live wire?

A

230V.

27
Q

What does the live wire carry?

A

Alternating potential difference from the supply.

28
Q

What colour is the neutral wire?

A

Blue.

29
Q

What is the potential difference of the neutral wire?

A

0V.

30
Q

What does the neutral wire do?

A

Completes the circuit.

31
Q

What colour is the earth/safety wire?

A

Green and yellow striped.

32
Q

What is the potential difference of the earth/safety wire?

A

0V.

33
Q

What is the function of the earth/safety wire?

A

To carry current, only if there is a fault.

34
Q

What is the earth/safety wire connected to?

A

The earth and the casing.

35
Q

What is power?

A

Energy transferred per second.

36
Q

What 2 things is power directly proportional to?

A

Current and voltage.

37
Q

What is the equation for energy transferred?

A

Energy transferred= power x time or energy transferred = charge x potential difference.

38
Q

What energy is transferred in a motor?

A

Kinetic energy.

39
Q

What energy is transferred in a kettle?

A

Thermal energy.

40
Q

What is work done in appliances?

A

When charge flows through a circuit (and is equal to energy transferred) and all energy is transferred to the appliance.

41
Q

What is the power rating of an appliance?

A

The power the appliance uses in watts.

42
Q

The higher the power rating…

A

The more energy the appliance uses.

43
Q

What is the national grid?

A

A system of cables and transformers linking power stations to consumers across the UK.

44
Q

What do step-up transformers do?

A

Increase the potential difference from the power station to the national grid.

45
Q

In step-up transformers, as power is constant…

A

Current decreases so less energy is lost.

46
Q

What do step-down transformers do?

A

Decrease the potential difference from the national grid to consumers for their safety.

47
Q

When 2 insulators are rubbed together…

A

~Electrons are transferred from one object to another
~This forms a positive charge on one object and a negative charge on the other

48
Q

Why do sparks occur?

A

When a charge jumped through the air from a highly negative object to a highly positive object to try balance the charges.

physics (7 decks)

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