year 10 eoy exam Flashcards
electricity: what is current measured in?
amps/amperes (A)
electricity: what is charge measured in?
coulombs (C)
electricity: what is energy and work measured in?
joules (J)
electricity: what is resistance measured in?
ohms (Ω)
electricity: what is time measured in?
seconds
electricity: what is voltage measured in?
volts (V)
electricity: what is power measured in?
watts (W)
what is insulation and how does it protect the user?
insulation is when the wires are covered in a insulating material and protects the user by preventing them touching the current-carrying wire, so it lowers the risk of electrocution
what is double insulation and how does it protect the user?
they have insulated wires and a non-metallic casing which acts as a second layer of protection. double insulated devices do not need to be earthed as the insulating casing cannot be electrified so there is less/no risk of electrocution for the user
what is earthing and how does it protect the user?
if an appliance with a metal casing has the live wire come into contact with the casing, it will be electrified and anyone who touches it could be electrocuted. an earth wire is an additional layer of protection in case this happens, as if the metal case gets electrified, the earth wire will provide a low resistance path to the earth, and it will get a surge of current, which means there will be a surge in current in the live wire too. the high current causes the fuse to melt and break and so the circuit is broken, so there is no more electricity going to the appliance, so there is no risk of electrocution
what is a fuse and how does it protect the device?
it is a safety device that is designed to break the circuit if the current becomes to high. it contains a thin wire which will melt if the current goes above a certain value, which isolates the appliance and prevents damage to the device. if the fuse melts, it has to be replaced
what is a circuit breaker and how does it protect the device?
a circuit breaker is designed to break the circuit if the current is too high. it has an push switch which is spring loaded. if the current is too high, the electromagnet will push the switch down by pulling the bolt of the switch (which holds the push switch in place). this will break the circuit, and so it isolates the appliance and prevents the risk of damage to the appliance. they are more reliable and sensitive than fuses, and do not to be replaced, only reset
why does a current in a resistor result in an increase of temperature?
the energy transfer is a result of electrons colliding with the lattice of atoms in the metal. the metal that the current is flowing through is made of a lattice of ions which are hit by the current of electrons flowing through. when the electron collides, it gives up some energy to the ions in the metal, which causes them to vibrate more and heat up
what are the uses of the increase of temperature in a resistor as the result of current?
it is used in electric heaters, electric hobs, electric ovens, toasters, kettles
what is the relationship between power, current, and voltage?
P=IV
power = current x voltage
(watt = amps x volts)
what is the relationship between energy transferred, current, voltage, and time?
E=IVt
energy transferred = current x voltage x time
(joules x amps x volts x seconds)
what is the difference between alternating current (AC) and direct current (DC)?
alternating current: current (or voltage) constantly changes direction continuously
direct current: current (or voltage) travels in one direction only
is electricity from mains supply AC or DC?
AC
is electricity from a cell or battery AC or DC?
DC
what are the advantages of a series circuit?
- fewer wires (so it’s cheaper and easier to assemble)
- uses less power
what are the advantages of a parallel circuit?
- components (for example bulbs) may be switched on or off independently
- if one component breaks, current can still flow through the other parts of the circuit
- bulbs maintain a similar brightness
how does voltage affect current in a series circuit?
as voltage increases, so does current
how does the number of components in a series circuit affect current?
in general, the more components in a series circuit, the lower the current
what happens to the current when you change the resistance?
when resistance increases, current decreases
how does the resistance of an LDR vary with light intensity/illumination?
as illumination/light intensity increases, resistance decreases
how does the resistance of a thermistor vary with temperature?
as temperature increases, resistance decreases
what is one way to indicate the presence of a current in a circuit?
adding a bulb/LED into the circuit
what is the relationship between voltage, current, and resistance?
V=IR
voltage = current x resistance
(volts = amps x ohms)
what is current?
rate of flow of charge
what is the relationship between charge, current, and time?
Q=It
charge = current x time
(coulombs = amps x seconds)
what is electric current in solid metallic conductors?
the flow of negatively charged electrons
what does current do at a junction in parallel?
it splits and then comes back together when the paths meet again
what does voltage do in parallel?
it stays the same for each path
what does voltage do in a series?
it splits for each component
what does current do in a series?
it stays the same over each component
what is voltage?
energy transferred per unit charge passed
what is a volt?
a joule per coulomb
what is the relationship between energy transferred, charge, and voltage?
E=QV
energy transferred = charge x voltage
(Joules = coulomb x volts)
waves: what are angles measured in?
degrees
waves: what is frequency measured in?
hertz (Hz)
waves: what is distance measured in?
metres (m)
waves: what is speed measured in?
metres/second (m/s)
waves: what is time measured in?
seconds (s)
what is a longitudinal wave?
a wave that oscillates along the direction of travel
what is a transverse wave?
a wave that oscillates perpendicular to the direction of travel
what is the definition of amplitude?
the maximum displacement of a wave from its undisturbed position
what is the definition of a wave front?
it is an imaginary surface representing points of a wave that are at the same point in their cycle
what is the definition of frequency?
the number of waves passing a given point in a second
what is the definition of a wavelength?
the distance from a point on a wave to the same point on the adjacent wave (eg peak to peak, or trough to trough)
what is the definition of a time period?
the time it takes for one complete wave to pass a certain point
do waves transfer energy?
yes
do waves transfer matter?
no
do waves transfer information?
yes
what is the relationship between wave speed, frequency, and wavelength?
v=fλ
wave speed = frequency x wavelength
(m/s = Hz x m)