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31 Cards in this Set
- Front
- Back
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rms for an alternating voltage |
The direct voltage which dissipates the same amount of energy as AC |
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rms for alternating current |
The rms value of AC is the direct current which dissipates the same amount of energy as AC |
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Photoelectric effect |
The process whereby electrons are ejected from a metal surface when light of a suitable frequency is incident on that surface |
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Threshold frequency |
The minimum frequency of light needed to emit electrons from a certain metal surface |
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Work function |
Minimum energy that an electron in the metal needs to be emitted from the metal surface |
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Ohm's law |
The potential difference across a conductor is directly proportional to the current in the conductor at constant temperature |
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Power |
Rate at which work is done |
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Cost of electricity |
Power (kW) × time (hours) ×cost per unit (Rand) |
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Internal resistance |
The resistance inside any battery needed to move the charge though the battery |
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Coulomb's law F=kQ1Q2÷r² |
The magnitude of the electrostatic force exerted by point charge Q1 on another point charge force Q2 is directly proportional to the magnitudes of the charges and inversely proportional to the square of the distance (r) between them |
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Electric field |
A region of space in which an electric charge experiences a force |
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Electric field at a point E=F÷q |
The electrostatic force experienced per unit positive charge placed at that point |
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Doppler effect |
Change in frequency (or pitch) of the sound detected by a listener because the sound source and the listener have different velocities relative to the medium of sound propagation |
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Positive work |
Forces parallel to an object's displacement |
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Negative work |
Forces anti-parallel to the object's displacement |
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Work-energy theorem Wnet=△K=Kf-Ki |
The work done on an object by a net force is equal to the change in the object's kinetic energy |
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Conservative force |
A force for which the work done in moving an object between two points is independent of the path taken |
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Non-conservative force |
A force for which the work done in moving an object between two points depends on the path taken |
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Principle of conservation of mechanical energy |
The total mechanical energy in an isolated system remains constant |
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Power P=W÷△t |
Rate at which work is done or energy is expended |
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A projectile |
An object upon which the only force acting is the force of gravity |
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Momentum p=mv |
The product of an object's mass and it's velocity |
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Linear momentum |
A vector quantity with the same direction as the velocity of the object |
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Newtons 2nd law in terms of momentum Fnet=△p÷△t |
The net force acting on an object is equal to the rate of change of momentum of the object in the direction of the net force |
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Impulse |
The product of the net force acting on an object and the time the net force acts on the object |
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Isolated system |
One in which the net external force acting on the system is zero |
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Principle of conservation of linear momentum |
The total linear momentum of an isolated system is conserved |
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Newton's 1st law |
A body will remain in its state of motion until a net force acts on it |
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Newton's 2nd law |
When a net force acts on an object, the object will accelerate in the direction of the force and the acceleration is directly proportional to the force and inversely proportional to the mass of the object |
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Newton's 3rd law |
When one body exerts a force on a second body, the second body exerts a force of equal magnitude in the opposite direction on the first body |
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Newton's Law of Universal Gravitation |
Each body in the universe attracts every other body with a force that is directly proportional yo the product of their masses and inversely proportional to the square of the distance between their centres |
