Karteikarten
AQA Physics: A2 Unit 4
Karten in diesem Stapel (50)
- 1Define: conservation of momentumIn any collision or explosion, total momentum remains constant provided no external forces act.
- 2Define: elastic collisionNo kinetic energy is lost
- 3How are force and momentum related?Force = rate of change of momentum
- 4What is meant by 'impulse'?The product of force and time
- 5Define the term 'radian'1 radian is the angle subtended by a circle of radius r by an arc of length r
- 6Define: angular speedThe angle in radians turned through in 1s
- 7Give 3 factors that affect centripetal forcemass
speed
radius (of circle) - 8What conditions must be satisfied for an object to be in SHM?1. The acceleration of the object is proportional to its displacement from the equilibrium position.
2. The acceleration is always directed back towards the equilibrium position. - 9Energy in SHM is the interchange between which two energy formsKinetic and potential
- 10How is the oscillations of a simple pendulum and a mass-spring system affected if taken to the Moon?simple pendulum - longer time period
mass-spring - no effect - 11What is a free vibration?System displaced and left to oscillate at its natural frequency
- 12What is a forced vibration?System driven at frequency other than natural frequency
- 13What happens when a system is driven at its natural frequency?Resonance
Amplitude of oscillations increases - 14What is damping?Resistive force that causes amplitude of oscillations to decrease
- 15What is critical damping?System returns to equilibrium as quickly as possible without 'overshooting'
- 16State Newton's gravitational lawGravity is an attractive force between point masses that is proportional to the product of the two masses and inversely proportional to the square of the distance between them
- 17What do gravitational field lines show?The direction a small test mass would move when placed in the gravitational field
- 18Describe in one word the gravitational field around a planetRadial (inwards)
- 19What is an equipotential?A region / surface of constant potential
- 20Define: gravitational field strengthThe force per unit mass acting on a small test mass placed in a gravitational field
- 21Define: gravitational potentialThe energy required to bring a unit mass from infinity to some point in a gravitational field, this is work done by gravity
- 22Why is gravitational potential a negative value?Work is done to reach infinity at which point gravitational potential is zero
- 23What is the gradient of a gravitational potential vs. distance graph equal to?Gravitational field strength
- 24Define: electric field strengthThe force per unit charge acting on a small positive charge at that point
- 25What is the unit for electric field strength?Newton per Coulomb or Volt per metre
- 26What is the unit for gravitational field strength?N / kg
- 27Define: electric potentialThe work done in bringing a unit positive charge from infinity to that point
- 28How do you find the electric potential difference between two points in an electric field?The work done in moving a unit positive charge from the point at the lower potential to that at the higher potential
- 29What is the unit for electric potential difference?Volt, V
- 30What is the electric field strength equal to in a uniform field?E = V / d
- 31What is the force F on a charge q equal to in an electric field of field strength E?F = qE = qV / d
- 32Describe the motion of a charged particle entering a uniform electric field perpendicular to the field linesparabolic
- 33Give one difference between electric and gravitational fieldsAct on charges instead of masses
or
Can be attractive or repulsive, g fields are only attractive - 34Define capacitancecharge stored / potential difference
- 35Define the Farad, F1 Coulomb stored when a p.d. of 1 Volt is applied
- 36What does the area under of a graph of Q against V represent?Energy stored
- 37What does the gradient of a graph of Q against V represent?Capacitance
- 38What is the time constant of a capacitor equal to?RC
- 39After how many time constants is a capacitor considered to be charged or discharged?5
- 40Define: magnetic flux densityForce per unit current per unit length
- 41Fleming's left hand rule: State what the 3 fingers representFirst finger: B field
Second finger: Current
Thumb: Force - 42Fleming's right hand rule: State what the 3 fingers representFirst finger: B field
Second finger: Current
Thumb: Force - 43Why does a particle moving in a circular path not spiral inwards?Force is perpendicular to the velocity at any time
The force causes a change in direction, but not a change in the magnitude of the velocity
No work is done in the direction of the force - 44State Lenz's lawThe direction of the induced EMF is such that the current it causes to flow opposes the change which causes it
- 45Define: magnetic flux and state the unitProduct of B and A
Webers, Wb - 46Define: magnetic flux linkage and state the unitProduct of the number of turns on a coil and the magnetic flux (NBA)
Unit: Weber-turns - 47How is the induced EMF and the flux linkage related?Rate of change of flux linkage = magnitude of induced EMF
- 48Describe how a p.d. is induced across the secondary coil of a transformerAn alternating p.d. across the primary coil produces an alternating magnetic field in the iron core.
This is linked to the secondary coil.
An alternating p.d. is induced across the secondary coil. - 49Describe how the efficiency of a transformer is maximised.The core is made from iron which can be magnetised and de-magnetised quickly.
The core is laminated, reducing eddy currents.
Low resistance wire is used for the coils, reducing the heating effect of the current. - 50Why is electricity transmitted at high potential differences?High p.d. means low current.
Low current means less energy transferred to the surroundings, increasing efficiency
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- Flashcards for AQA A level Physics Unit 4
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