Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Unit 3B - Forces And Electromagnetism > Flashcards

Unit 3B - Forces And Electromagnetism Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
0
Q

Is you apply a larger force on a spanner causing a turning effect would it mean a larger or smaller moment?

A

Larger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

How do you work out the moment?

A

Moment = force x perpendicular distance from the line of action of the force to the pivot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

To get the maximum moment you need to push at right angles to the moment why would pushing at any other angle mean a smaller moment?

A

Because the perpendicular distance between the line of action and pivot is smaller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the centre of mass?

A

The point at which the whole mass is concentrated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

The centre of mass hangs directly below?

A

The point of suspension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What experiment can you do to find the centre if mass of any flat shape?

A
  1. ) suspend the shape and a plumb line from the same point and wait until they stop moving
  2. ) draw a line along the plumb line
  3. ) do the same things again but suspend the shape from a different point
  4. ) the centre of mass is where the two lines cross
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

If the anticlockwise moments equal the clockwise moments the object is?

A

Balanced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Total anticlockwise moments = ?

A

Total clockwise moments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Levers used the idea of balanced moment to make us easier to do what?

A

Do work e.g. lift an object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do levers work?

A

Levers increase the distance from the pivot, meaning less force is needed to get the same moment meaning it is easier to lift stuff

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are levers known as and why?

A

Force multipliers because they reduce the amount of force that’s needed to get the same moment by increasing the distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Name three examples of simple levers.

A

Long sticks, wheelbarrow and scissors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

If the total anticlockwise moments do not equal the total clockwise moments there will be?

A

A resultant moment and so the object will turn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do the most stable objects have?

A

A wide bass and a low centre of mass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

When will an object begin to be unstable and tip over?

A

When the centre of mass and line of action of weight moves beyond the bade as it will cause a resultant moment and it will tip over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can a simple pendulum be made?

A

By suspending a wight from a piece of string,when you pull back a pendulum and let it go it will swing back and forth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why a is time period in a pendulum?

A

The time taken for the pendulum to swing from one side to the other and back again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the same for each swing or a pendulum?

A

The time period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can you calculate time period?

A

Time period = 1 / Frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the time period of a pendulum depend on?

A

The length of it, the longer the pendulum the greater the time period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If the centre of mass acts beyond the pivot in a bid what will happen?

A

The bus will fall over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Can you compress a liquid?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does it mean by liquids being virtually incompressible?

A

You can’t squash them, their volume and density stay the same

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

As liquids are in im incompressible and can flow what can happen?

A

A force applied to one point in the liquid is transmitted to other points in the liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What can you say about how much and in which direction pressure is transmitted in liquids?

A

Pressure in liquids is transmitted equally in all directions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How can you figure out pressure in hydraulics?

A

Pressure = force / area over which force is applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is pressure measured in?

A

Pascals (Pa)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is force measured in?

A

Newtons (N)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does in mean by hydraulic systems are used we force multipliers?

A

They use a small force to produce a bigger force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How does a hydraulic system work?

A

It uses two pistons one with a smaller area and one with a larger area, as pressure is transmitted equally through the liquid the pressure at both piston is equal. So at the 1st piston a pressure is exerted on the liquid using a small force over a small area, the pressure is then transmitted it the 2nd piston. The 2nd piston has a much larger area and so as force = pressure x area, there will be a larger force produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Name four things that hydraulic systems are used in?

A

Car braking systems, hydraulic car jacks, manufacturing and deployment of landing gear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What happens when an object is travelling in a circular motion?

A

It is constantly changing direction, which means its velocity is constantly changing so the object is accelerating, the acceleration is towards the centre of the circle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

I’m circular motion what must be acting on a object to cause acceleration?

A

A resultant force, the force acts towards the centre of the circle, the force that keeps something moving is called a centripetal force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What three things can cause of centripetal force?

A

Fraction, tension or even gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What happens is the centripetal force stops?

A

The object will go off at a tangent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Where does the centripetal force come from when a bucket is whirling around on a rope?

A

The tension in the rope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What three things does centripetal force depend on?

A

Mass, speed and radius

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What happens to a centripetal force the faster a object is?

A

The centripetal forge has to be bigger to keep the object moving in a circle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What happens to the centripetal force the lather the mass of an object?

A

The bigger the centripetal force is as it has to be to keep the object moving in a circle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Do you need more or less forge to keep something moving in a smaller circle and why?

A

More because it has more turning to do

40
Q

What three things cause a bigger centripetal force?

A

More speeds, more mass and a smaller radius

41
Q

What is the definition of a magnetic field?

A

A magnetic field is a region where magnetic materials (like iron and steel) and also wires carrying currency experience a force acting on them

42
Q

Which way to the arrows on the field limes point?

A

From the North Pole of the magnet to the South Pole

43
Q

A magnetic field is created through what type of wire?

A

One carrying a current

44
Q

What can you used to show the direction of the magnetic field around a current carrying wire?

A

Your right hand thumb, your finger represent the current and your fingers represent the direction of the magnetic field

45
Q

What is acceleration?

A

A change in velocity

46
Q

Is the magnetic field inside a coil of wire weak or strong?

A

Strong

47
Q

What is the magnetic field like outside of a coil of wire?

A

Like magnetic fields around a bar magnet

48
Q

What is another name for a coil of wire?

A

Solenoid

49
Q

If you add a magnetically soft iron core through the middle of the coil what do you get?

A

An electromagnet

50
Q

How easily can a magnetically soft material magnetise and demagnetise?

A

Very easily

51
Q

What about their magnetism makes electromagnets really useful?

A

It can be switched on and off

52
Q

How do you turn off an electromagnet?

A

Turn off the current so the magnetic field and it’s magnetism stops

53
Q

What machines uses an electromagnet?

A

Cranes in scraps yards and steel works

54
Q

Why are electromagnets useful in cranes?

A

Because they can be turned on and off, if you were to use a normal magnet the crane would pick stuff up but then wouldn’t put it down so it wouldn’t be very useful

55
Q

Name two things that can effect the size of an electromagnet?

A

Number of turn of wire, the size of the current going through the wire

56
Q

Passing an electric current through a wire produces?

A

A magnetic field around the wire

57
Q

What is the force experiences by a current carrying wire in a magnetic field known as?

A

The motor effect

58
Q

What happens when you put a wire into a magnetic field?

A

You will have two magnetic fields combining, which puts a force on the wire

59
Q

Which direction do magnetic fields travel?

A

From north to south

60
Q

Which direction does the force that a wire experiences when put in a magnetic field go in relation to the wire and the magnetic field?

A

At 90 degrees and so perpendicular to both

61
Q

What happens to the force the a wire experiences in a magnetic field if the direction of current in the wire or the magnetic field is reversed?

A

Then the force is also reversed

62
Q

What force does a wire experience if it runs along parallel to the magnetic field?

A

It won’t experience any force

63
Q

Does wire have to be at 90 degrees to a magnetic field to experience a force?

A

No at 90 degrees the wire will experience full force but at angles in between 90 degrees and 0 it’ll feel some force but not it all

64
Q

What can you use to tell you which way the force acts on a wire through a magnetic field?

A

Flemings left hand rule

65
Q

How does the Fleming’s Left Hand rule work and what can it tell you?

A

Your first finger points in the direction of the field, your second finger points in the direction of the current and your thumb will point in the direction of the force

66
Q

What do you do with your hand for the Flemings Left Hand Rule?

A

Point your thumb upwards and your first finger perpendicular to that like a gun and then point your second finger so that it is perpendicular to both your thumb and first finger

67
Q

How can you remember what each finger tells you in Flemings Left Hand Rule?

A

First Finger represents Field
seCond finger represent current
thumb represents what is left and so force

68
Q

What effect do electric motors use?

A

The motor effect

69
Q

What two factors speed up an electric motor?

A
  1. ) more current

2. ) stronger magnetic field

70
Q

What does a split ring commutator do and why?

A

It swaps the contacts every half turn to keep the motto running in the right direction

71
Q

How can you reverse the direction of a motor?

A

Swapping the polarity of the direct current, so from positive to negative to positive to negative or by swapping the magnetic poles over

72
Q

Name six things electric motors are used in?

A

CD players, food mixers, fans, drills, hair dryers and cement mixers

73
Q

How can an electric motor be used in a fan?

A

You link the coil of wire to an axle, and so as the coil rotates so does the axle and so if there’s a fan attached to the axle it rotates as well

74
Q

How does an electric motor work?

A

There is a coil of wire inside a magnetic field, and so the forces acting on each arm of the coil of wire are opposite. As the forces act one up and one down it causes the coil to rotate. After a half turn the contacts are swapped so that the motor continues to rotate in the same direction instead of rotating back

75
Q

What is electromagnetic conduction?

A

The creation of a potential difference across a conductor which is experiencing a change in magnetic field

76
Q

What is another word for induction?

A

Creation

77
Q

What two ways can you induce a potential difference in a wire?

A
  1. ) by moving a magnet in a coil of wire

2. ) by cutting magnetic field lines with an electrical conductor

78
Q

What happens to the potential difference and current if you move the magnet in the opposite direction or reverse the polarity of the magnet?

A

Both the potential difference and current will be reversed

79
Q

How is an alternating current created with a magnet in a coil of wire?

A

If you keep moving the magnet backwards and forwards, you induce a potential difference that keeps swapping direction producing an alternating current

80
Q

How does a generator work?

A

As you turn a magnet in a coil of wire the magnetic field through the coil changes, inducing a potential difference which makes a current flow in the wire, when you have turned a magnet a half turn the direction of the magnetic field reverses as the poles are turning, this creates a reversing potential difference and so the current begins to flow on the opposite direction creating an alternating current

81
Q

What is an example of a device that uses electromagnetic induction to generate a current?

A

A dynamo

82
Q

If the current flows from right to left in a coil of wire which direction are the magnetic field lines inside and outside the coil of wire?

A

Inside the coil they go towards where the current is coming from so left to right, and outside the coil they go opposite and so right to left

83
Q

How is a dynamo used to power lights in a bike

A

The wheel turns it turns the cog, which is attached to a magnet in a coil. So as the cog and magnet turns it induces a potential difference and current which is used to power the lights

84
Q

How does a transformer work?

A

An alternating current in the primary coil produces a changing magnetic field in the iron core. This produces a changing magnetic field around the secondary coil. As these field lines cut the field lines of the secondary coil it induces an alternating potential difference across the end of the secondary coil through electromagnetic induction. If there is a complete circuit an alternating current will then flow out through the secondary coil

85
Q

What type of current do transformers have to be in?

A

Alternating current?

86
Q

Why can’t transformers use direct current?

A

They need the alternating current to produce a changing magnetic field and in the primary coil and so in the iron core. And so in the secondary coil to induce a potential difference, a direct current wouldn’t do this

87
Q

What does a transformer look like?

A

They have two coils of wire joined together by an iron core

88
Q

What are the names for the two types of coil in a transformer?

A

Primary and secondary

89
Q

What are the two different types of transformer?

A

Step up and step down

90
Q

Whats the difference between the amount of coils on a step up and a step down transformer?

A

A step up transformer has more turns on the secondary coil where as a step down has more turns on the primary coil

91
Q

Does the iron core carry the current or magnetic field?

A

Magnetic field not electricity flows in the iron core

92
Q

How efficient are transformers?

A

100%

93
Q

In a transformer power in = ?

A

Power out

94
Q

What are switch mode transformers?

A

They’re a type of transformer that operates at higher frequency that traditional transformers

95
Q

Between what frequency can switch mode transformers work at?

A

Between 50kHz and 200 kHz

96
Q

Why are switch mode transformers made at a much higher frequency?

A

They can be made much lighters and smaller than traditional transformers

97
Q

Name two things that switch mode transformers are used in?

A

Mobile phone chargers and power supplies

Physics (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions