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End of year science yr9 > Physics > Flashcards

Physics Flashcards

1
Q

What is electric current

A

Electric current is the flow of charge around a circuit

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2
Q

Can circuits’ energy flow if their incomplete?

A

No, a circuit had to be complete to work

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3
Q

What are the moving charges?

A

The moving charges in a circuit are negative electrons

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4
Q

What is convention current?

A

Conventional current is electron current which behaves as though it is positive charges that causes current flow, because it travels from the positive terminal to the negative, where as regular charge flows the opposite way

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5
Q

Is current ever used up?

A

No, current is never used up as it flows through s constant circuit. The total current in the circuit is always the same

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6
Q

What is potential difference across a circuit?

A

Potential difference in a circuit is the energy that flows between two points in a circuit

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7
Q

How is potential difference measured?

A

Potential difference is measured in volts, and if you add the voltage of each component in series, that gives you the voltage of the whole power supply

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8
Q

How do you calculate potential difference?

A 
Potential difference can be calculated across a component using ohms law:
Potential difference (V)= current (I)xresistance(R)
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9
Q

How is ohms law applicable to current and resistance?

A

Ohms law can be applied to both current and resistance as follows:
Current (I)=potential difference (V) ÷ resistance (R)
Resistance=potential difference (V) ÷current (I)

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10
Q

What is resistance in a circuit?

A

Resistance is anything in a circuit that slows down the flow of current.

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11
Q

What is resistance measured in?

A

Resistance is measured in ohms (Ω)

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12
Q

What does resistance mean in a circuit?

A

In a circuit as long as the potential difference stays the same, the higher the resistance of a component, the smaller the current that flows through it.

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13
Q

What do you call components and materials that electricity can pass through?

A

Conductors. Metals are the best form of these.

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14
Q

What are insulators?

A

Insulators are components or materials that don’t easily allow electricity to pass through them if at all (like wood).

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15
Q

Why are insulators good heat stores?

A

Because they trap the heat energy in itself as they do not allow free electrons to pass through them and transfer energy easily like conductors. So good conductors of electricity are bad ones of heat.

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16
Q

How can you tell which components in a circuit are better conductors?

A

The lower the resistance of a component, the better it is at conducting electricity because more electrons are being permitted to pass through easily.

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17
Q

What is the role of ammeters in a circuit?

A

Ammeters measure electric current around the circuit.

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18
Q

What is current measured in?

A

Current is measured in amperes (amps for short). You measure the current through a circuit by inserting the ammeter into the battery and the bulb. But because current didn’t get used up, the current through the ammeter’s the same as through the bulb

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19
Q

What is used to measure potential difference?

A

To measure potential difference voltmeters are used. Potential difference is measured across something in a circuit like a bulb.

20
Q

What are potential difference ratings in batteries and bulbs?

A

A battery potential difference rating tells you the potential difference it will supply across the circuit. A bulb rating tells you the maximum potential difference that you can safely put across it for it to work.

21
Q

What is a series circuit?

A

A series circuit is a circuit where the current has no choice of route and every part of the circuit is on the same path.

22
Q

Can any part of s series circuit be on or off at a given time?

A

In series circuits the current is either on or off- the switch being open or any other break in he circuit will stop the current flowing everywhere, like in fairy lights

23
Q

Is the current different in any part of a series circuit?

A

No, the current in a series circuit is the same throughout the circuit as the current has no choice of route, which is another reason why the circuit breaks if one component is lost.

24
Q

How is potential difference portrayed in the battery (or cell) of a series circuit?

A

In series circuits, the potential differences across each of the components add up to the total potential difference of the whole cell.

25
Q

What are parallel circuits?

A

In parrallel circuits, the current has a choice of where it is distributed across the circuit

26
Q

Why will ammeter readings in a parallel circuit be different to eachother?

A

Because when current in a parallel circuit flows out of the cell and through the first ammeter, it may have two or three different directions it can travel to distribute current, so if you have 3 bulbs and five ammeters the readings on each are different to eachother

27
Q

What happens to the dum of the current after it has passed through multiple bulbs in a parallel circuit?

A

When current has been distributed across each bulb and it has been read on each ammeter, the overall current passing from each bulb meets up at the end of the circuit at one individual ammeter, so the sum of the ammeter’s readings on the bulbs will equal the amount on the ammeters at the end

28
Q

Can some bulbs in a parallel circuit be on and the others be off?

A

Yes, if the bulbs have switched you can open the switch to a bulb (which severes the current flowing through it) and the other bulbs would still remain on with their switches closed because the current has a choice of where to glow still

29
Q

Is the potential difference in each bulb in a parallel circuit still equal to the potential difference in the cell like in a series circuit?

A

Yes, even the bulbs that are turned off in a parallel circuit still have a potential difference output, so the sum won’t be thwarted

30
Q

What is static electricity?

A

a stationary electric charge, typically produced by friction within negatively charged electrons and postitively charges protons, which causes sparks or crackling or the attraction of dust or hair.

31
Q

What is gravity?

A

Gravity is the force that attracts a body towards the centre of the earth, or towards any other physical body having mass. That is why planets such as the earth and moon are in orbit to the sun- they are attracted by gravity. The larger the object, the stronger the force of gravity( that’s why planets with a large mass have higher gravity). Also, the longer the distance between objects the weaker the gravitational attraction becomes.

32
Q

What is mass?

A

Mass in objects is the amount of matter in an object without any forces or anything acting on it. The mass of an object never changes, no matter where in the universe it is.

33
Q

What is weight caused by?

A

The pull back of gravity

34
Q

Does an object retain its weight no matter the planet it’s on?

A

An object has the same mass whether it’s on earth or any other planet, but it’s weight will be different according to the gravitational pull of that planet or star.(eg: something weighing 1kg will weigh less on mars (about 3.7N) than on earth (about 10N) because the force of gravity pulling on it is less.

35
Q

What is weight?

A

Weight is a force motivated by gravity which is measured in Newtons (N). It’s measured using a spring balance or newton meter.

36
Q

Is mass a force?

A

Mass is not a force. It’s measured in kilograms (kg) with a mass balance which stays the AMA won any planet

37
Q

What is the formula for calculating weight?

A

Weight=mass+gravitational field strength

W=mXg
( the weight is in newtons, the mass in kilograms and the gravitational field strength is in Newton kilograms (N/kg))

38
Q

What is the weight in newtons of a 5kg mass both on earth and mars?(weight formula example)

A

A:
W=mXg
On earth: W= 5 x 10= 50N(the weight of the kg mass is 50N)

On Mars: W= 5 x 3.7= 18.5N ( the weight of the 5kg mass is 18.5N)

39
Q

What is sound?

A

A sound wave is the pattern of disturbance caused by the movement of energy traveling through a medium (such as air, water, or any other liquid or solid matter) as it propagates away from the source of the sound. The source is some object that causes a vibration, such as a ringing telephone, or a person’s vocal chords

40
Q

What are longitudinal waves?

A

Longitudinal waves have vibrations that are parallel to the direction of the sound wave. This means the vibrations are also parallel to the the direction of energy transfer

41
Q

What are examples of longitudinal waves?

A
  1. Sound waves

2. A slinky spring when you push the end( because there are vibrations in the same direction as the wave is travelling)

42
Q

How does sound travel?

A

Sound travels as a longitudinal pressure wave

43
Q

What are sound waves caused by?

A

Vibrating objects

44
Q

What does sound need to travel?

A

Sound needs a medium ( eg: air or water) to travel through because something has to pass on the sound vibrations.

45
Q

How are the sound vibrations passed through the medium?

A

Via a series of compressions ( regions of squashed up particles)

46
Q

Why can’t sound travel in space?

A

Sound can’t travel in space because it’s mostly a vacuum so there are no particles to act as a medium

End of year science yr9 (3 decks)

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