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AQA GCSE Physics > higher content > Flashcards

higher content Flashcards

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1
Q

What is inertia?

A

The idea that without an unbalanced force, nothing will change in terms of speed, direction etc.

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2
Q

How is inertial mass defined?

A

By the ratio of force over acceleration

if an object is more inert then it’s harder to move

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3
Q

When will a seesaw balance in terms of moments?

A

When the anticlockwise moment is equal to the clockwise one

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4
Q

What does the principle of moments state?

A

For a balanced object, clockwise moments = anticlockwise moments

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5
Q

What is the centre of mass of an object?

A

The point at which the mass may be thought to be concentrated

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6
Q

Where does the centre of mass lie in symmetrical objects?

A

Along the line of symmetry

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7
Q

Where will the COM be when an object has more than one line of symmetry?

A

Where the lines of symmetry intersect

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8
Q

Where will the centre of mass be of a suspended object?

A

The centre of mass will be directly below the point of suspension

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9
Q

How can the COM of an irregular shape be found?

A
  • by hanging the shape from a point and a plumb line is used to draw a vertical line downwards from the pivot
  • this is repeated from different points
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10
Q

What is the stability of an object affected by?

A
  • the width of the base of the object

* the height of it’s centre of mass

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11
Q

When will an object not topple over?

A

When the line of action is within the base

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12
Q

What are the three types of equilibrium when a force is applied to objects?

A
  • stable equilibrium - tilts and falls back to original position
  • unstable equilibrium - tilts and falls
  • neutral equilibrium - rolls
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13
Q

What happens to the centre of mass when a stable object is tilted?

A

It is raised

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14
Q

What happens to the centre of mass when an unstable object is tilted?

A

It is lowered

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15
Q

What happens to the centre of mass when a neutral object is tilted?

A

It stays at the same level if pushed

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16
Q

What is the equation for momentum?

A

Mass x velocity

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17
Q

What is momentum measured in?

A

kgm/s

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18
Q

Why will a ball be harder to stop if it has a large mass and moving at a high speed?

A

There will be a greater force exerted on the person’s hands by the ball. They will have to exert an equal and opposite force on the ball to stop it

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19
Q

What happens to momentum in a collusion of explosion?

A

Momentum is conserved, provided that there are no external forces having an effect

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20
Q

What are the external forces that could have an effect on momentum?

A
  • friction which decreases momentum

* gravity (e.g. a collision on a slope)

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21
Q

What does Fleming’s left hand rule show?

A

The direction of movement of the wire

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22
Q

What does each finger represent in Fleming’s left hand rule?

A
  • index finger - direction of field from N to S
  • middle finger - direction of current from + to -
  • thumb - direction of movement
23
Q

How is the direction of the force in an electromagnet reversed?

A
  • reversing the direction of the current

* reversing the direction of the magnetic field

24
Q

What is 1 tesla equal to?

A

1 newton per amp per metre

25
Q

What equation is used to calculate the force on a wire?

A

F=BIL

26
Q

What is the motor effect?

A

When a wire is placed in a magnetic field and experiences a force

27
Q

How does a d.c. motor work?

A

When a coil of wire is placed in a magnetic field and therefore the two sides of the coil experience a force due to the motor effect

28
Q

Why does the coil rotate in a d.c. motor?

A

The current of the opposite side of the coil is in the opposite direction, so the forces are in opposite directions

29
Q

Where are split ring commutators used?

A

In electric motors

30
Q

How do split ring commutators work?

A

Every half turn it breaks the current so the coil of wire keeps turning in the same direction

31
Q

What is an easy way to tell if a setup is a motor or a generator?

A

A motor will have a battery, a generator will not

32
Q

What is the generator effect?

A

The induction of a potential difference in a wire which is moving relative to a magnetic field

33
Q

How is a voltage induced in a wire using the generator effect?

A

• if a wire is moved downwards to cut through the magnetic field

34
Q

When is a voltage not induced using the generator effect?

A
  • if the wire is stationary

* if the wire is moved parallel to the field line

35
Q

How is the voltage induced increased using the generator effect?

A
  • move the wire faster

* use a stronger magnet

36
Q

How is the voltage induced reversed in a wire?

A
  • move the wire in the opposite direction

* reverse the magnetic field

37
Q

During electromagnetic induction, why do you have to do work when you push the magnet into the coil?

A

The electromagnet is repelling the magnet so energy is transferred

38
Q

During electromagnetic induction, why do you have to do work when you pull the magnet out of the coil?

A

The electromagnet is attracting the magnet so work is done against the force

39
Q

What happens when a magnet is moved into a coil of wire which is a part of a complete circuit?

A

A current is induced in the wire - the coil is now an electromagnet

40
Q

What is purpose of slip rings in an a.c. generator?

A

So the wire doesn’t twist as the coil rotates

41
Q

What is the energy transfer in an electric generator?

A

Kinetic to electrical

42
Q

What is the energy transfer in an electric motor?

A

Electrical to kinetic

43
Q

What is an a.c. generator also known as?

A

An alternator

44
Q

What is a d.c. generator also known as?

A

A dynamo

45
Q

Why does an alternator produce an a.c. output?

A
  • the two sides of the coil are always connected to the same side of the lamp
  • when the LHS of the coil moves past the top it reverses the direction of movement
  • so voltage and therefore current reverses
46
Q

Why does a dynamo produce a d.c. output?

A
  • the two sides the coil are connected to split rings so the two sides of the coil are not connected to the same side during a turn
  • every half turn the connections are reversed so when induced voltage is reversed, the current flowing is not reversed
47
Q

How does a microphone work?

A
  • a magnet is moved near a coil and a current is generated so the diaphragm is attracted to coil
  • diaphragm vibrates in response to incoming sound waves and coil vibrates
  • this induces a current in the coil (a.c.)
48
Q

What is a transformer made of?

A

A primary and secondary coil wrapped around an iron core

49
Q

Why is the iron core of a transformer laminated?

A

So no induced currents flow in the iron core

50
Q

What does it mean when an iron core is laminated?

A

It is made in layers of iron

51
Q

How does a transformer work?

A
  • a current flows in the primary coil and becomes an electromagnet
  • this magnetises the iron core which is linked to the secondary coil
  • a.c. voltage - magnetic field inside secondary coil will keep changing size and direction so a voltage is induced in the secondary coil
  • voltage will change direction and br an a.c. current
52
Q

What does the size of a secondary voltage in a transformer depend on?

A
  • primary voltage

* number of turns on each coil

53
Q

What is the equation to work out the voltage or number of turns in a transformer?

A

Vp/Vs = Np/Ns

AQA GCSE Physics (13 decks)

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