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86 Cards in this Set
- Front
- Back
- 3rd side (hint)
Mass (Kg) vs Weight (N)
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Weight is a force on an object that is in a gravitational field where as
Mass is the amount of matter in an object. |
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F = ma
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where;
F = force m = mass (Kg) a = acceleration (m/s) |
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Gravitational Field
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- shows the direction a smaller mass would move if placed near a large mass
- field lines point towards a massive object - On Earth's surface the gravitational field lines are uniform |
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W = mg
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where;
W = weight in N m = mass in kg g = acceleration due to gravity (9.8m/s-⒉ on Earth) |
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Factors affecting acceleration due to gravity (g)
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- Height, as height increases g decreases
- Density, points of higher density will also have slightly higher g - Mass/Radius, larger mass and smaller radius will have a larger g |
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Newtons Law of Universal Gravitation
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- Any object that has mass, has gravity
- Larger objects have stronger gravitational fields thus more noticeable gravity |
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Magnitude of Gravitational attraction, where:
G = universal gravitational constant m = mass (kg) r = distance from centres (m) F = force (N) |
F = G m① x m②
----------- r⒉ |
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Gravitational Potential Energy (GPE)
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The work done to move an object from a very large distance away to a point in a gravitational field
- GPE is ALWAYS negative - If we raise and object, it gets more GPE |
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E*p = - G m① x m②
----------------- r |
where;
E*p = potential energy (J) [Joules] G = universal gravitational constant m = mass (Kg) r = distance from centres (m) |
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GPE at infinity distance away from any gravitational field.
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- Has a GPE of 0 joules/ is no longer in a gravitational field
- Brought closer than infinity away it has less than o GPE but is now in a gravitational field |
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Projectile Motion
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- Follows a parabolic path.
- Can be split into vertical and horizontal components. - Vertical velocity at the peak is 0 m/s -Horizontal velocity stays constant (V = u) |
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Equations for Projectile Motion
where; s = displacement u = initial velocity V = final velocity a = acceleration t = time |
V⒉= u⒉ + 2as
s = ut + ½ a t⒉ v = u + a t |
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Range and Launch Angle
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- At 45∘ a projectile will achieve it's maximum range.
- an angle of < 45∘ will give a projectile more horizontal velocity but less time in the air (because it doesn't have the height) - an angle of > 45∘ will give a projectile more time in the air, but less horizontal velocity |
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.The velocity at which an object on the surface of a body must be propelled in order not to return to that body under the influence of their mutual gravitational attraction
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Escape Velocity - definition
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Escape Velocity
V*e = √ ( 2G m*planet ------------- r*planet ) |
- Does not depend upon the mass of the object trying to escape
- Newton's idea for escape velocity came from projective motion |
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G - forces
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a persons apparent weight as a multiple of their true weight
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- experienced when a person accelerates (changes velocity)
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Human limitations in relation to G-forces.
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A person can withstand between ~ ≤10 g
(this causes blood to rush towards the feet and the person may black out) |
and ≥ -3 g
(this causes the blood to rush to the head and burst a capillary causing bleeding to the brain) |
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Rockets are launched:
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with the rotation of the Earth so they have the additional rotational velocity.
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Uniform Circular Motion
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is circular motion with a constant speed.
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a*c = v⒉
-------- r |
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Centripetal force
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always acts towards the centre of the circle.
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F*c = mv⒉
--------- r |
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Kepler's law of periods
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r⒊ = Gm
T⒉ 4π⒉ Calculates orbital velocities |
- Period is in seconds,
- radius in metres and - radius is the distance between the centres of the object in orbit and the heavenly body it is orbiting (altitudes needs the radius added to it) |
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Elliptical orbits are _ shaped
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oval
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Satellites in a low Earth orbit; (LEO) - [higher than 250km, lower than 1000km]
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move fast and can slow down due to atmospheric drag and crash to Earth
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Satellites in a Geostationary orbit;
(where the period of the satellite is 24hrs) |
remain above the same position relative to the Earth's surface
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If the angle of re-entry is too high __
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a spacecraft will burn up due to the heat produce on re-entry
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If the angle of re-entry is too low __
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the spacecraft will 'skip' or bounce off the atmosphere and back into space and may not have enough fuel to re-enter again.
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Ionisation Blackout occurs during re-entry, it is __
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a period where no radio communication occurs because of ionised particles around the shuttle
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The heat from re-entry ionises the air particles around the spacecraft.
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G-forces can be problematic for astronauts during re-entry, if the angle of entry is more vertical then __
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the deceleration is greater and the g-forces experienced are also greater.
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The sling shot effect is a manoeuvre designed to __
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increase or decrease the velocity of a satellite or spacecraft.
- the satellite gets dragged by the planets orbital motion |
The satellite goes behind the planet to increase velocity
and in front of the planet to decrease velocity |
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An inertial frame of reference is __
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a frame of reference that is in constant motion or stationary
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it is impossible to distinguish between a stationary frame of reference and a frame of reference in constant motion without obseving another frame of reference
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A non-inertial frame of reference is __
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a frame of reference that is not in constant motion or stationary (i.e it is accelerating)
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If you are on a moving platform and throw a tennis ball forward, the tennis ball will have the throwing speed plus the platform speed as observed by a stationary observer.
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You observe the tennis ball move at only the throwing speed because you are in motion with it.
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This is Newtonian relativity (but light doesn't conform to it - light is a hipster)
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The Aether Model states that the properties of the aether are:
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* It was the medium that light propagated through*
- The aether filled all of space - It has a low density - It was perfectly transparent - it was perfectly non viscous - It was very stiff, allowing light to travel very fast through it |
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Michelson - Morley Experiment
aimed to _ |
find the relative motion of the aether.
They did this by racing two light beams, one with the aether and one across at 90∘ to the aether. |
When the two light beams met at the interferometre if they were out of phase then the light would destructively interfere, if in phase they would constructively interfere.
- The experiment found that there was no relative motion of the Earth to the aether. |
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Einstein's theory of light states that __
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- Light travels at the same speed in all frames of reference.
- Light does not need a medium to travel through, it is self propagating. - If light travels at the same speed in all frames of reference then distance and time will be different in both frames of reference. |
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Relativity of simultaneity states that __
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- Simultaneous eventsin one frame of reference are not necessarily simultaneous in another frame of reference.
also |
- Both observers are correct in their observations (even if their observations seen contradictory)
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In a moving frame of reference, time dilates - equation
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t*v = t*o
----- √ 1-(v⒉/c⒉) |
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In a moving frame of reference, time:
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- appears to run as normal as seen from this frame of reference
- on Earth time runs faster as seen from this frame of reference |
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In a stationary frame of reference, time:
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- appears to run as normal as seen from this frame of reference
- in a moving object runs slower as seen from this frame of reference |
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Experiment to test the relativity of time:
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Two atomic clocks are syncronised, one remains stationary while the other is placed in a high speed jet. The atomic clock in the jet travels at high speeds for a period of time and brought back to rest. The two atomic clocks are compared and the one that was in the high speed jet has 'lost time'.
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The length of a moving object contracts (it gets shorter) - equation
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ℓ*v = ℓ*o √ [1-(v⒉/c⒉)
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In a moving frame of reference, length:
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- appears as normal as seen from this frame of reference
- length of the Earth is shorter as seen from this frame of reference |
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In a stationary frame of reference, length:
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- appears as normal as seen from this frame of reference
- length of a moving object is shorter as seen from this frame of reference |
No experiment to test this as of yet.
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The mass of a moving object dilated (it gets heavier) - equation
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m*v = m*o
----- √ 1-(v⒉/c⒉) |
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Experiment to test relativity of mass:
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Beta particles (electrons) that are emitted from a radioactive source travel at speeds of near the speed of light.
Results: |
When the q to m ratio of these beta particles is measured it is different to that of a slower electron. When the beta particles speed is factored into the equation it's q to m ratio is the same as other electrons.
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Relativity of simultaneity states that __
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- Simultaneous eventsin one frame of reference are not necessarily simultaneous in another frame of reference.
also |
- Both observers are correct in their observations (even if their observations seen contradictory)
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In a moving frame of reference, time dilates - equation
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t*v = t*o
----- √ 1-(v⒉/c⒉) |
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In a moving frame of reference, time:
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- appears to run as normal as seen from this frame of reference
- on Earth time runs faster as seen from this frame of reference |
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In a stationary frame of reference, time:
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- appears to run as normal as seen from this frame of reference
- in a moving object runs slower as seen from this frame of reference |
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Experiment to test the relativity of time:
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Two atomic clocks are syncronised, one remains stationary while the other is placed in a high speed jet. The atomic clock in the jet travels at high speeds for a period of time and brought back to rest. The two atomic clocks are compared and the one that was in the high speed jet has 'lost time'.
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The length of a moving object contracts (it gets shorter) - equation
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ℓ*v = ℓ*o √ [1-(v⒉/c⒉)
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In a moving frame of reference, length:
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- appears as normal as seen from this frame of reference
- length of the Earth is shorter as seen from this frame of reference |
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In a stationary frame of reference, length:
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- appears as normal as seen from this frame of reference
- length of a moving object is shorter as seen from this frame of reference |
No experiment to test this as of yet.
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The mass of a moving object dilated (it gets heavier) - equation
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m*v = m*o
----- √ 1-(v⒉/c⒉) |
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Experiment to test relativity of mass:
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Beta particles (electrons) that are emitted from a radioactive source travel at speeds of near the speed of light.
Results: |
When the q to m ratio of these beta particles is measured it is different to that of a slower electron. When the beta particles speed is factored into the equation it's q to m ratio is the same as other electrons.
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E = mc⒉
As an object is accelerated some of the __ (work) used to accelerate it is changed into __ this is why it is impossible to go faster than the speed of light (__), because you can't put in infinite __ to accelerate an object of infinite __. |
energy, mass, (3x10⒏m.s-⒈), energy, mass.
- If mass is destroyed as it is in a nuclear explosion, that mass is changed into __. |
energy.
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The Twins Paradox says that when two twins, one stationary and one moves away at near the speed of light and comes back - what happens?
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The moving twin is younger, than the stationary twin that remains on Earth.
If we observe this situation from the moving twin's frame of reference, s/he is __ and the twin that remains on Earth is __ so the aging effects should be __ but it is not. - why? |
stationary, moving, reversed
This is because one is in an inertial frame of reference (the stationary twin) the other is in a non-inertial frame of reference (not constant speed)(the moving twin). |
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Magnetic field lines go from __ to __.
The number of field lines represents the __ of the magnet. (x) represents __ the page ⨀ represents __ of the page. |
north, south,
strength, into, out |
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Magnetic field lines never cross, except __
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in a galvanometre (radical magnetic field).
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The magnetic field around a current carrying conductor is found by the __
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right hand grip rule (thumb points in the direction of conventional current).
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Conventional current flows from _ to _.
Electrons flow from _ to _. |
'+' (positive) '-' (negative)
'-' (negative) '+' (positive) |
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A solenoid is __
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a coil of wire that makes a magnetic field (more coils, stronger field).
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The motor effect
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When a current is placed in a magnetic field it will experience a force.
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The direction a current carrying conductor will move when place in a magnetic field can be determined by __
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the right hand palm rule.
Where: thumb indicates __ fingers show __ palm moves __ |
direction of conventional current (I).
magnetic field lines (B). in the direction of the force it experiences (F). |
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Factors that affect the magnitude of the force on a current carrying conductor are:
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- Strength of the magnetic field.
- Amount of current flowing through wire - Angle between conductor and magnetic field (elaborate) - Length of the conductor |
If the angle of the wire is parallel to the field lines then the force experienced is zero.
If the wire is at 90∘ to the field lines then the force it experiences is a maximum. |
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Calculate force using equation -
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F = B I ℓ sinθ
where: |
F = force (N)
B = magnetic field strength (T) I = current (A) ℓ = length of the conductor in magnetic field (m) θ = angle between conductor and the field lines (∘) |
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Parallel wires that have current flowing in the __ direction will attract.
Parallel wires that have current flowing in the __ direction will repel. |
same
opposite |
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Factors that affect the force on parallel conductors:
F = k x I①x I② ℓ ---- d |
F = force on wire (N)
ℓ = parallel length of conductors (m) k = 2x10-⒎ magnetic force constant I① = current through wire ① I② =current through wire ② d = distance between wires (m) |
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The main parts of a DC motor are:
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Stator - the stationary part of the motor (usually the magnets)
Rotor - the rotating part of the motor (usually the coil) Split Ring Commutator - a ring that allows the current to be reversed Brushes - allows contact from the power to the commutator |
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Torque is __
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a turning force.
t = Fd t = torque (N.m) F = force (N) d = distance (m) |
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Calculating torque in a motor equation -
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t = nBIAcosθ
where: |
t = torque
n = number of coils B = magnetic field strength (T) I = current (A) A = area of the coil (m⒉) θ = angle relative to magnetic field |
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When a conductor is moved relative to a magnetic field __
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then an electric current is produced.
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Magnetic flux is __
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a measure of the amount of magnetic field permeating a space - measured in weber (Wb)
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Magnetic flux density is __
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the amount of magnetic flux passing through a square metre - measured in tesla (T) - also known as magnetic field strength
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- magnetic flux = flux density x area
- flux density = magnetic flux/area |
ɸ = BA
B = ɸ/ A |
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An eddy current is a __ current induced in a conductor that is in a __ magnetic field. The direction of the eddy current can be determined using the ___.
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circular
changing right hand grip rule |
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Eddy currents need a ___. If there is no ___ then their size is restricted.
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connecting pathway
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__ motors have a ___ commutator, allowing the direction of the current to be changed so that the motor can continue to spin.
__ motors have a ___ commutator because the direction of the current is already changing so it doesn't need to be changed. |
DC, split ring
AC, slip ring |
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A generator uses __ energy to make __ energy. A motor is the same in structure as a generator but __ in what we do with it.
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kinetic
electrical opposite |
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Transformers are:
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devices that increases or decreases AC voltages
Consisting of: |
a primary coil and a secondary coil wound onto a soft iron core.
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To calculate primary and secondary voltage equation -
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-- V(primary) = n(primary)
V(secondary) n(secondary) where: V = voltage n = number of coils |
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High current means __ energy changed into heat.
Low current means __ energy changed into heat. |
more
less |
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Step Up Transformers make output voltage __ than the input voltage.
Step Down Transformers make output voltages __ than the input voltage. |
greater
less - explain the use of each |
Step up used to transmit electricity across large distances so energy loss is minimised.
Step down used to run in houses for most appliances. |
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Like DC motors, DC generators and AC generators, AC motors are made with a __ and a __.
Most AC motors use a ___ commutator and have a ___ rotor that rotates around the axis of the shaft. |
rotor, stator, slip ring, cylindrical.
*The slip rings used in AC motors (and generators) consists of two full rings which are __ connected to one end of the coil. - What does this do to the direction of the current? |
permanently.
*This ensures that as AC input changes, the direction of the current flow through the coil remains constant and so will the direction of the torque. |
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How does an induction motor work?
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By using a changing magnetic field to induce a current in the rotor.
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A ____ consists of a number of conducting bars joined together by 'end rings'
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'squirrel cage'
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