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Physics P456 > P5 > Flashcards

P5 Flashcards

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1
Q

What is an atom made up of?

A

charged particles.

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2
Q

What are between charged objects?

A

electrostatic forces.

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3
Q

What is an example of electrostatic forces?

A

hair standing up when it attached to a charged comb.

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4
Q

The outermost electrons are less…

A

strongly attracted to the nucleus.

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5
Q

What does a variable resistor do?

A

A device that allows you to control the current by changig the resistance wire.

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6
Q

Resistance=

A

Voltage (in volt)s / current (in Amps)

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7
Q

What is a series circuit?

A

When the components are connected in a line.

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8
Q

In a series circuit, the current is..

A

The same through all the components.

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9
Q

How can the outermost electrons in static electricity be removed?

A

By rubbing

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10
Q

What happens when two insulating objects are rubbed together? Why?

A

They become charged. This is because electrons are transferred from one object to the other.

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11
Q

What happens when you brush your hair?

A

Individual hairs become similarly charged and repel each other, making your hair stick up.

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12
Q

What happens when you take off a nylon or polyester top?

A

Electrons move through the air from the negatively charged clothing to your positively charged hair.

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13
Q

What builds up during a thunderstorm? What is the effect of this?

A

Charge, which flows between the cloud and the Earth as a flash of lightning.

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14
Q

Why are metals good conductors of electricity?

A

Because they have free electrons, which means there are lots of charges free to move.

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15
Q

Why are plastics electrical insulators?

A

Because there are few free electrons in the plastics, which means there are few charges free to move.

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16
Q

When the bulb is lit in a circuit…

A

there is an electric current.

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17
Q

In a complete circuit…

A

there are free electrons in all the metal components and connecting wires.

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18
Q

The flow of charge is the…

A

electric current.

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19
Q

What is electric current?

A

the rate of flow of charge.

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20
Q

What is electric current measured in?

A

Amperes.

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21
Q

The more energy the charged particles receive from the power supply..

A

the greater the current.

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22
Q

In an electric current..

A

charge is conserved and energy is transferred.

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23
Q

What is used to measure current?

A

An ammeter.

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24
Q

What is the unit for voltage?

A

volt.

25
Q

The larger the voltage of the battery in a circuit…

A

the bigger the current.

26
Q

What is voltage?

A

The measure of how much energy is supplied to the circuit and how much energy is transferred in the component.

27
Q

Power=

A

voltage x current

28
Q

What does a voltmeter measure?

A

the difference in energy between the terminals of a battery and a bulb.

29
Q

What is potential difference (p.d)?

A

The difference in energy per unit.

30
Q

The more resistance in a circuit…

A

the lower the current.

31
Q

The greater the voltage across a resistor..

A

the larger the current.

32
Q

What is resistance?

A

a measure of how much a conductor opposes the current.

33
Q

What is a variable resistor?

A

a device that allows you to control the current by changing the amount of resistance in a circuit.

34
Q

Resistance=

A

Voltage (in volts) / Current (in amps).

35
Q

A graph of voltage against current will give you…

A

a straight line through the origin.

36
Q

The higher the resistance in a graph…

A

the lower the gradient.

37
Q

In a series circuit, is the current the same or different through all the components connected?

A

The same

38
Q

The more cells connected in a series…

A

the greater the potential difference.

39
Q

The p.d across the components in a series circuit will be proportional to..

A

its resistance.

40
Q

What is a thermistor?

A

A semi conductor whose resistance changes with temperature.

41
Q

What is a light dependent resistor?

A

A semiconductor whose resistance changes as the amount of light falling on i changes. In bright light, the resistance will be low.

42
Q

What is a magnetic field?

A

a space around a magnet in which a magnetic force acts.

43
Q

Where is the magnetic field strongest?

A

Where the field lines are closest together.

44
Q

When is a voltage induced?

A

When a magnet is moved near a piece of wire.

45
Q

When is a current ALWAYS induced?

A

When there is relative movement between the magnet and the coil of wire.

46
Q

When is the direction of current reversed?

A

When the motion of the wire is reversed, so the magnet turns around.

47
Q

When will current increase?

A
  • a stronger magnetic is used
  • the speed of motion increases
  • there are more turns of wire in the coil
48
Q

When is there a continuous supply of electricity produced?

A

When there is a continuous relative motion between the magnet and a coil of wire.

49
Q

When is a larger voltage induced?

A
  • the strength of the magnet is increased.
  • the number of turns in the coil is increased.
  • the rate at which the coil is turned increased.
  • an iron core is used inside the coil.
50
Q

The faster the rate of cutting field lines…

A

the larger the induced voltage.

51
Q

How is mains electricity produced?

A

By generators in power stations that induce an alternating voltage.

52
Q

As a coil rotates in a uniform magnetic field..

A

…it cuts the lines of magnetic field at different rates.

53
Q

When the coil is at a right angle to the field lines…

A

…it cuts no field lines so the induced voltage is zero.

54
Q

When the coil is parallel to the field lines…

A

…its rate of cutting field lines is at a maximum, so the inducted voltage is at a peak.

55
Q

As the coil rotates…

A

it cuts field lines in a different direction, so the direction of the voltage alternates.

56
Q

What is direct current (d.c.)?

A

Current that always flows in the same direction. E.g. batteries.

57
Q

What is alternating current (a.c.)?

A

Current that changes direction at regular intervals.

58
Q

What are transformers used for?

A

to step up the voltage at the power station and to step down the voltage near near our homes.

59
Q

Why is the UK’s electricity supply a.c?

A

Because it is easier to generate a.c current in large amounts.

Physics P456 (2 decks)

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