Technology in Space Flashcards
EMF - Electric Motor Force
the total energy that it (power supply) suppliers to each coulomb of charge - push of the cell
Current
the rate of flow of charge
Conservation of charge
charge is not created or destroyed it is conserved
Potential difference
energy used by a coulomb to pass a component - energy per unit charge
Adding resistors in parallel
reduces the total resistance of the circuit
Series circuit
current the same, p.d shared
Parallel circuit
p.d same, current shared
Resistance –> Current
the more easily charge can flow, the lower its resistance and the greater the current will be for a given voltage
What happens if you increase the resistance?
needs more energy to get through the components so p.d increases as cell gives some of its internal resistance to the circuit
Lost volts
- internal resistance in the cell
- the energy needed to go through the cell
- you can never measure the true EMF with a voltmeter over a component due to this
Power
the rate at which energy is transferred
When will you get maximum power output?
when the load resistance equals the internal resistance however the efficiency will decrease and only 50% will be useful
Negative temperature coefficient
as the temperature increases the resistance decreases - exponential ddecrease
Positive temperature coefficient
as the temperature increases the resistance increases - linear
Explain a PTC
resistance is collisions between electrons and positive lattice ions –> the temperature increases so the lattice ions vibrate more causing more collisions and therefore more resistance
Explain a NTC
- usually semiconductors so no delocalised (free) electrons
- as the temperature increases they become better conductors as electrons become delocalised so the resistance decreases but as they become delocalised they begin to become a PTC
Drift Velocity
some particles can move when a p.d is applied - negative particles move to positive terminal and vice versa forming a current
Gold leaf experiment
- the rod is positive so when placed near the plate it will attract free electrons to the top
- this means the bottom will be positive and the top will be negative
- because the bottom and the gold leaf have the same charge they will repel each other raising the gold leaf
Gold leaf: 1 photon is absorbed
by 1 electron (giving it enough energy to leave meaning the gold leaf falls as it is discharged)
Gold leaf: What effect does ultra violet light have?
- it can cause the gold leaf to fall immediately if there’s a negative charge on the plate
- if the plate is positive or red laser light is used, these have no effect
Gold leaf: How does the ultra violet light work?
gives the photoelectron energy when absorbed meaning the photoelectron has enough energy to leave –> this means ultraviolet light is not just a wave but a particle
Ultraviolet light is a wavicle
-this means it is in between a wave and a particle –> sometimes it has wave properties and sometimes it has particle properties depending on the situation
Work Function
the minimum amount of energy needed for the electron to leave the surface (changes from metal to metal)
How does the intensity affect the photons released?
more photons are released
