Unit 2 Definitions Flashcards
Define the watt
The watt is the SI unit of power and is equivalent to one joule transferred per second
State that the efficiency of a device is always less than 100% because of heat losses
^^
Define the joule
The SI unit of work or energy and is equal to the energy transferred when one Newton is moved one meter
electric current is: the net flow of charged particles
the net flow of charged particles
The charge carriers in a metal are?
The charge carriers in an electrolyte are?
Electrons
Ions
Explain what is meant by conventional current and electron flow
Conventional flow is from positive to negative
Electron flow is from negative to positive
Define the coulomb
Charge = current x time
The coulomb is the SI unit of charge.
1 coulomb = 1 amp second
State what is meant by drift velocity
Mean drift velocity is the average velocity that charge carriers (electrons) move down the wire
Define potential difference
P.d. Is the energy transferred per coulomb of charge from electrical energy to other forms
Define the volt
1 volt = 1 joule / 1 second
Define EMF
Emf is the energy transferred by the supply, per unit charge from other forms, to electrical
Describe the difference between EMF and Pd in terms of energy transfer
Emf is the energy transferred by the supply, per unit charge from other forms, to electrical
Pd is the energy transferred per coulomb of charge from electrical energy to other forms
Define resistance
Resistance is a measure of the opposition a material exerts against the flow of electrons
Define the ohm
1 ohm is the resistance when the ratio of p.d. Across a component to current through it is 1 volt per Amp.
State ohms law
Current is an ohmic conductor is proportional to the voltage across it
(Provided temperature and other physical conditions are constant
Define the resistivity of a material
Resistivity is an inherent property of a material. It depends of the atomic structure and temperature of the material.
Define the kilowatt hour (kWh) as a unit of energy
1 kWh is the equivalent of 1000 watt hours
Or
3.6 mega joules
State kirchoff’s second law and appreciate that this is a consequence of conservation of energy
Kirchoff’s second law:
- Based on the law of conservation of energy
- A circuit loop must contain an emf and a p.d.
- I.e. A power source and some form of component
Explain the meaning of the term ‘terminal p.d.’
Terminal p.d. Is the voltage is available to the circuit (what is coming out of the battery), not just what the battery says on the tin.
Define displacement of a wave
Displacement is the distance a particle moves from its central equilibrium position
Define the amplitude of a wave
Amplitude is the maximum displacement from the central equilibrium position
Define path difference
Path difference is the extra distance travelled by waves from one source compared to another
Define time period of a wave
Time period = 1/frequency
But, the period of a wave is the time for a particle on a medium to make one complete vibration cycle.
